# A Survey on Wireless Body Area Networks for eHealthcare Systems in Residential Environments
## 5 Summary of Recent Research Articles
### Survey Results  
Among the articles that are included in Table 14, seven articles consider off-body (ambient) sensors along with on-body sensors [118; 119; 127; 137; 140]. In many of these articles, a data fusion technique is used to integrate multiple data sources into meaningful information. The other 28 articles investigate only on-body sensors [109; 110; 111; 112; 113; 114; 115; 116; 128; 129; 130; 131; 141; 142]. Moreover, half of the articles employ mobile devices such as smart phones or PDAs as base stations. 16 articles out of 35 articles used classic Bluetooth as the main wireless communication technology [109; 110; 111; 113; 122; 123; 128; 130; 131; 133; 138; 139; 141; 142; 143]. Therefore, classic Bluetooth is considered as the most popular technology among the included articles. On the other hand, 14 studies used ZigBee as the main wireless communication technology [114; 115; 116; 118; 120; 121; 122; 123; 124; 125; 126; 127; 128; 129; 132; 133; 135; 137; 139]. Therefore, ZigBee is considered as the second most popular technology among the included articles. However, surprisingly, in none of the included studies BLE is used, which is likely to be explained because BLE is a relatively recent technology.  
Five articles out of 35 articles as shown in [110; 111; 121; 129; 121] focus on fall detection systems based on various sensor types and different techniques, whereas, four articles of the articles that are listed in Table 14 [111; 113; 119; 142] concentrate on Activities of Daily Living (ADL) of patients and elderly people. A few of these articles also investigate specific chronic conditions such as anxiety [112], chronic obstructive pulmonary and chronic kidney [138] and Parkinson's disease [109; 116].  
Thirsty articles out of 35 articles that are listed in Table 14 used one of the popular wireless technologies such as Bluetooth or ZigBee. Some of the systems reviewed in Table 14 as shown in [112; 117; 119; 134; 139; 142] use WiFi protocol for wireless communication. However, according to many studies such as [143; 144; 145; 146; 147; 148], WiFi technology has shown that it is more power-hungry than Bluetooth technology. Thus, these systems appear to have high power requirement especially when compared to home-based eHealthcare system requirements. When power is of little concern, the choice of wireless is less critical and designers usually choose ones they are familiar with, easy to implement or in certain scenarios ones which fit with existing infrastructure (WiFi, GSM, _etc._). A home environment eHealthcare system has tight restrictions on power consumption, which therefore rule out many protocols including WiFi and classic Bluetooth, or even ZigBee. There is however a distinct lack of application of alternative low- power wireless technologies or even BLE technology. This may be due to aforementioned need to interface with infrastructure or other devices.  
A true home-based patient monitoring system must be able to transparently monitor individuals in home environment over extended periods of time. In these systems, sensor power requirements are of utmost importance. Hence it is imperative that the employed wireless technologies have minimal power consumption. If the application and choice of communication technology allow, energy harvesting based operation has the potential to power the devices indefinitely. It is expected that in the years following this survey a large body of research will accumulate with systems utilizing devices that require no specific attention from those they monitor (_i.e._, charging). These systems would therefore allow devices to be worn in everyday clothing and be operating continuously.