# Implementation of Context Aware e-Health Environments Based on Social Sensor Networks
## 5 Social Sensor System Design and Discussion

Table 3: Features of emulated health and social sensors. figure shows five seconds of user's electrocardiogram signal. This health information is not usually analyzed by the user but instead a cardiologist in order to verify the heart activity and diagnose possible cardiac diseases, such as ventricular arrhythmias, atrial fibrillation, _etc._  
With regards to social sensors, temperature and relative humidity measurements are depicted in Figure 15c. As can be seen, temperature values range from 16 \({}^{\circ}\)C to 19 \({}^{\circ}\)C, and relative humidity from 35% to 38%, which could be usual in a home monitoring system. These measurements give the user and service provider relevant information about user's comfort and environment state during daily life conditions. Once again, ambient temperature and humidity values out of suitable comfort ranges could be representative of _Heating-Ventilation-Air-Conditioning_ (HAVC) system malfunction and/or its inappropriate control by the user. Finally, Figure 15d shows the number of times the hall door is opened/closed and how many time it has remained in each state. Although it does not provide specific user's information, its analysis could be useful for inferring behavior aspects and daily activities. In this case, it is possible to know the time when the user has left from/arrived to home, or some people have visited the user; the information even allows knowing the time period the hall door has stayed opened. As previously stated, the information gathered by the social sensors and the health sensors are processed by the back-end servers, where database processing as well user interfaces are implemented and managed. Figure 16 shows the implemented application layer, in which information such as monitoring of social sensors and health sensors, location of sensors within the household or detailed view of existing alarms can be obtained. The system is designed in order to provide a modular and easily accessible screen configuration to access relevant information, such as bio medical signal status and alarm monitors. Figure 15: (**a**) Weight measurements obtained from the Social Sensor network devices. (**b**) Electrocardiographic signal obtained from the Social Sensor network devices. (**c**) Temperature and relative humidity measurements. (**d**) Hall door opening and closing events. Figure 16: _Cont._  
The system has been developed in order to minimize the operation problems. In any case, the following are the main reasons for malfunction and detection mechanisms provided by the system to correct them. * Device malfunction or misuse: At any time, a medical device or social sensor can show a wrong operation; even when that device has a proper operation, it can be misused by the user or caregiver. The service provider staff must detect these situations in order to solve the problem, by either replacing the broken device or retraining the user/caregiver on the correct use. Thus, the NASISTIC system includes a log message module that registers the main activity performed by devices. These messages are transmitted to the back-end so they can be viewed and analyzed by technical worker. * False notifications: The system allows the configuration of alerts based on the received measurements in order to generate messages/notifications to those in charge of the user. During system operation, some occasional wrong measurement can be taken due to device malfunction/misuse or unusual environment conditions, which will generate false alerts. Obviously, there are acquisition parameters (e.g., temperature and humidity) that allow analyzing measurement trends in order to detect occasional out of range data. In this way, the system rejects the data and does not generate a false alert. Other acquisition parameters (e.g., gas, open-close, flood) require generating an alert in any case the measurement is out of range because it implies a hazardous situation.