## 1 Introduction  
The demand for smart healthcare services, which allow monitoring patients' health status in a pervasive and noninvasive manner, is increasing as a means to alleviate the issues associated with costly welfare systems and an increasing elderly population, as well as to improve quality of life, bringing benefits to patients, medical personnel, and society [1,2].  
As a result, outstanding research and development efforts have been carried out during the last years both by academia and industry in this area, driving great breakthroughs on enabler technologies, such as wireless communications, micro- and even nano-electronics, or sensing techniques and materials.  
Advances in microelectronics and wireless communications have made Wireless Sensor Networks (WSNs) and Body Area Networks (BANs), which represent two key functional components in smart healthcare systems, a reality, despite the fact they present different features.  
WSNs can be used to deploy low-cost and low-consumption communications infrastructure to support wide coverage and mobility (_i.e._, pervasiveness), enabling natural movement of patients as well as potential development of value- added services (e.g., Location Based Services--LBS).  
BANs are composed of tiny smart sensors deployed in, on, or around a human body [3]. Such sensors are deployed inside the human body in the so-called _In-Vivo_ or Implantable BANs (IBANs). This kind of networks is still in an early development stage. Currently, they are mainly based on very specific wireless communications technologies, such as MICS [4]. In the long-term, they may be based on nanonetworks, a completely novel communications paradigm that aims at copying natural molecular and cell communications [5,6]. These sensors are distributed on the human body, measuring different physiological parameters, in the so-called Wearable BANs (WBANs), which represent the most widely used solution within this scope nowadays. Smart fabrics that combine conductive materials with organic textiles (e-textiles) are of special interest to the so-called WBANs, since they provide a comfortable and user-friendly way to monitor patient's health status over extended periods of time, avoiding the use of cables wired around the patient.  
This paper is mainly focused on architectures and communications technologies for smart healthcare systems based on WBAN (so-called Wearable Healthcare Monitoring Systems--WHMS).  
The remainder of the paper is structured as follows: Section 2 elaborates on typical architectures, features, and available communications technologies for wearable healthcare systems: In addition, Section 2 comprehensively surveys related work in this area. Section 3 uses the LOBIN platform to illustrate how e-textiles and WSN can be combined to develop smart healthcare systems providing not only real-time physiological monitoring but also additional services such as indoor location. Section 3 also compares the platform developed and the results obtained in the context of the LOBIN project with the related work presented in previous section. Section 4 discusses the most appropriate design criteria and decision making depending on the specific requirements of the target applications. Finally, Section 5 summarizes the paper and draws conclusions.