# A Survey on Wireless Body Area Networks for eHealthcare Systems in Residential Environments
## 1 Introduction  
The ageing population around the world has been rapidly growing as a result of increased longevity, mainly attributable to the substantial improvement in nonwithstanding, medicine and public health. In the United Kingdom alone, the population over the age of 85 is predicted to nearly triple by 2035 [1]; in the United States, the population over the age of 65 is estimated to double by 2040 [2]; in the People's Republic of China, the population over the age of 60 is expected to double by 2040 [3]; and by the year 2050 Japan will have the eldest population in human history, with an average age of 52 years [4].  
Simultaneously, public-funded healthcare systems in many developed countries are currently confronting an increase in the number of people diagnosed with chronic diseases such as obesity and diabetes. These chronic illnesses are not simply a result of ageing population but are due to inappropriate diet, sedentary lifestyle and insufficient physical activity [5; 6]. As reported by the World Health Organization (WHO), diabetes is estimated to become the seventh leading cause of death by 2030 [7]. Due to its chronic nature, diabetes is an expensive illness not only for individual patients but also for healthcare systems as well.  
These estimates and statistics indicate the fact that, continuously providing healthcare services to patients who are diagnosed with chronic conditions and increasing number of elderly people with various health difficulties is significantly increasing the cost of healthcare systems [8; 9; 10].  
Therefore, healthcare systems are becoming unsustainable in their current form [9; 11]. According to scientists [12; 13; 14; 15], early disease detection and diagnosis is extremely important; on the one hand, it assists to effectively slow the progress of illness [13; 14; 15]; on the other hand, it helps to significantly reduce the cost of healthcare systems [12; 14].  
It is, however, possible to utilize the latest technological advances in Wireless Body Area Network (WBAN) systems along with Information and Communications Technologies (ICTs) for the early detection and prevention of potential diseases that may occur later in the people's lives [16; 17; 18]. This can be done by integrating ultra-low-power none-invasive and/or invasive sensor nodes into WBAN systems for continuous monitoring of health conditions [19]. Each node within a WBAN system is capable of capturing physiological data such as electrocardiogram (ECG), electroencephalography (EEG), respiratory rate, body temperature and movement and transmits the collected data either as raw samples or low-level post-processed information to a base station wirelessly in order to be further analyzed and processed [20]. A WBAN system is able to provide long-term health monitoring of people without limiting their daily activities [21]. Such a system can be utilized to develop an intelligent and inexpensive healthcare monitoring solution which can be used as part of a diagnostic process [22]. The future system will be able to remotely monitor elderly people and chronically ill patients in their own residential environments where they are most relaxed and comfortable, and to minimize expensive hospitalization costs and reduce frequent hospital visits [22].  
There are similar published studies in this area such as [23; 24] that investigate some aspects of WBAN research such as physical and data link layer, and also compare a number of low-power radio technologies. The primary contribution of this paper is to not only investigate and compare the existing low-power on-body communication technologies, but also to consider the requirements and challenges of these low-power wearable technologies to communicate with the home infrastructure. Therefore, this paper considers the applicability and practical use of the existing low-power wearable technologies in a residential environment.