Ambient Assisted Living an Overview of Current Applications, End-Users and Acceptance

Worldwide an ageing of the population can be observed. This imposes several problems on the concerning societies. There, a higher share of elderlies needs to be taken care of by a diminishing number in younger population. To still be able to provide sufficient care the use of technology is regarded as a solution. In this paper, we are examining the special field of Ambient Assisted Living (AAL) as an application of technology in health care. It mainly focusses on enabling independent living at home for people in need of care through technology. In detail, we aim at giving an overview of current applications, their end-users and their acceptance of AAL. We find that common applications of AAL are smart homes, sensors and robotics. The common end-user of these applications are elderlies. They have a positive opinion towards AAL in general but criticize their price and want to be included in the development process. Abbreviations: sisted an Overview of Current -plications, End-Usersand Acceptance.


Introduction
Ambient Assisted Living (AAL) is a research area, where the focus lies on enabling people with any kind of impairment to stay independent in their own home for as long as possible. To achieve this, Information and Communication Technologies (ICT) are used in various ways. The upcoming of Ambient Assisted Living can be regarded as the answer to several global trends. AAL technologies are expected to solve the problems that are imposed due to recent worldwide socio-economic developments. There, the ageing of the global population can be observed at first. Here, low birth rates stand opposite to a bigger share of elderly citizen with high life expectancies. At the same time, a decreasing supply in health care services results in rising costs for care. Also, a general increase of chronic diseases and the general will of elderly or impaired people to stay in their known environment puts pressure on the current health care systems of many nations. Therefore, Information and Communication Technologies have been a field of research and are expected to solve or to diminish the stated problems. Especially in the home environment, where AAL solutions are applied, the lack of formal caregivers can be decreased. Also, the visits to medics can be less frequently, because conditions might be detected early and thus, treatment costs can be decreased. The mentioned global developments increase the pressure on health care systems, the application of AAL technology is researched to ease these trends.
In this paper, we provide further background information on the causes that influenced the upcoming of Ambient Assisted Living in recent research as well as on the past evolution of these technologies. Furthermore, we conducted a literature review to give an overview about the following topics within the AAL domain.
These topics are: i.
The current applications in the AAL domain are regarded with a focus on technologies that try to increase the independence of its users. We conclude that smart home technology, stationary and wearable sensors as well as different types of robots are of special interest in this domain.

Background
The upcoming of Ambient Assisted Living from a socioeconomic perspective as well its terminology and evolution are regarded in this section. Firstly, four socio-economic trends are described.
Angeing Population: According to the United Nations [1] the population is ageing worldwide. By 2050 it is prospected that the total number of people aged 65 and older will surpass the group of adolescents with an age between 15 and 24. This development is mainly a result of low fertility and mortality rates. Countries where these two factors apply are in the so called third phase of demographic transition. There the population growth only minimal or zero to negative. In comparison, the first phase is defined by low population growth due to high fertility and mortality rates. In the second phase has fast population growth, decreasing mortality and still high fertility. The third phase of this development can be seen in Europe, North America and Australia. It is even expected that Latin America and Asia will reach this phase until the end of 21st century [2]. An exception in Asia are Eastern and South-Eastern Asia, were the third phase is already expected in 2038. Here, Japan  2050 it is expected to reach 50 [2]. This development is especially strong in Europe but some countries in Eastern-and South-Eastern-Asia are even expected to surpass a ratio of 50 [3]. As can be seen in ( Figure 1) the ratio might be as high as 70.9 in Japan until 2050 according to IMF data.
A similar but less dramatic trend can be seen in the USA Canada and Australia. Here, the ratio will have surpassed 40 but stays below 50 until 2050 [4]. These devices or systems can be simple sticks as walking aids, wheelchairs, adjustable beds or alarms for home security [11].
With the general technological progress these technologies became more advanced.
Especially, the development of ambient intelligence in combination with assistive technologies played a vital role in the upcoming of AAL. It uses recent advances in information technology to create digital environments that act as an electronic butler to the resident. To achieve this, ambient intelligence integrates sensor networks, to collect user and environmental data. The collected data is reasoned by the system to then perform actions which benefit the resident proactively in their daily life but in an unobtrusive manner [12]. If this paradigm of context aware computing, that integrates undistinguishable into the environment is used on the development of assistive technologies, this is called Ambient Assisted Living [13]. This view on the nature of AAL devices is especially adopted today because it makes use of the recent technological advances for example in artificial intelligence, machine learning or ubiquitous computing.
Ambient intelligence is the most recent paradigm of Ambient Assisted Living technologies. But before that AAL devices also existed. The emergence of Ambient Assisted Living technologies can generally be categorized into three generations [14].
i. The first AAL systems focused mainly on alarms in the form of wearable buttons. In the case of an emergency this button can be pressed by the user to call for help. ii.
In the second generation of devices the systems should not be dependent on the users' interaction but rather detect an emergency on their own. By using sensors, e.g. falls or gas leaks can be detected automatically.
iii. The third generation focusses not only on the detection and report of an incident but tries to prevent them.
Here the paradigm of ambient intelligence comes into use.

Materials and Methods
In this paper we aim at giving an overview of relevant topics within the AAL domain. Therefore, three relevant topics have been defined and formulated as the research questions of this paper.
These are: RQ1 What are the current applications of Ambient Assisted Living?
RQ2 Which end-users are the target group of Ambient Assisted Living applications?
RQ3 How is the acceptance of Ambient Assisted Living among its end-users?
To provide this overview we conducted a literature review in Technologies, review, overview has been selected as primary literature. Supporting, secondary literature has been selected based on the primary or through free searches in the stated engines. To answer RQ2 and RQ3 the primary literature was used or also a free search was conducted.In this paper, we aim to give an overview of AAL by reviewing overviews of this domain. Thus, it is possible to identify relevant topics that occur in these different publications.
In this way, this paper differs from other overviews that review individual AAL projects to identify trends or from publications providing a list of AAL projects that is limited to several topics.

Results and Discussion
In this section, we provide the results of the literature review for the individual research questions.

RQ1 What are the current applications of Ambient Assisted Living?
For the answer of the first research question several overviews of the AAL domain have been reviewed. Even though the applications of AAL to enable independent living for its user are diverse, three main topics were identified. These are Smart Home, Sensing and Robotics. Within these topics several approaches exist. These are highlighted through project examples in this paper.

Smart Home:
In the regarded overviews the smart home technology is often described as an AAL application since it enables independent living in the domestic environment.As a reason for this [15] states the diminishing health status of elderly or disabled people overtime, that is accompanied with the wish to stay independent in a familiar surrounding. Therefore, ICT solutions that integrate into the home provide a solution. [16] has even observed that within the AAL domain special home accessories and furniture are the most common devices. For that reason, also the smart home technology can be regarded as a major contributor to Ambient Assisted Living to enable more independency for its users. The importance of this technology can be also seen as the digitization of the domestic environment becomes more and more a point of focus for health management of patients [12]. In [17] the smart home is described as living environment that is digitized by sensors and smart appliances and thus forms a network that is capable to deliver automated services to the user based on his lifestyle. In order to deliver that services, the smart home uses various devices to firstly monitor the activities of the resident.
The smart home is then able to analyze the collected data about the resident's activities in his environment. Based on this analysis the digital environment can offer services tailored to the resident and assist him in his daily life. This is achieved through various components: sensors (e. g. motion sensors), household appliances (e.g. lights), actuators (e.g. door openers), security (e.g. password locks), communication (e.g.human machine interfaces).
The independence of a smart home resident in AAL can be achieved in various ways. A typical application in this context is described in [15] and can be seen in ( Figure 2). Here the elderly home is equipped with a sensor network that monitors the resident.
The sensor data is transmitted via WiFi to a base station that connects via a Gateway to the homes of peers, family or friends and to health care responsibles such as carers and doctors. In this way the health status of the resident can be continuously supervised.
In case of an incident or emergency fast care can be provided, via direct communication among the participants. Al Shaqi R et al.
describes three general categories that distinguish the ways how the resident of a smart home is assisted in his daily life e.g. through actuators or bycontributing to health care management. These three categories of AAL smart homes are: Figure 2: Typical Smart Home according to [15].
i. Smart homes that are assisting daily and social activities for example through providing orientation aid such as in [18].
ii. Smart homes that are improving the resident's safety for instance by predicting falls as in [19].
iii. Smart homes that asses the resident's health status through his vital parameters such as in [20]. The smart homes' ability to control daily tasks is further described in [14].
The two components are distinguished. First, there is the general health monitoring which comprises the systems and devices used to assess the inhabitants' health status. As a second, there are platforms that aim to integrate the several health systems, ensure interoperability and thus create the smart home environment.
According to the premise of AAL the assistance of theresident through smart homes must be intelligent, unobtrusive and ubiquitous [10]. This non-disrupting nature of domestic monitoring systems is also emphasized in [21,22]. These are static sensors to monitor the user from a fixed location and mobile sensors that can also be worn. Their overall aim is to recognize human activity which is then processed to provide AAL services.
According to this study, the various sensors are commonly used for home safety, home automation, activity monitoring, fall detection, localization and tracking and health status monitoring.
This study also provides an overview of sensors that are widely used in the Ambient Assisted Living domain.
Therefore, three different types of sensors are distinguished. can also be static e.g. by implementing them into the flooring. In that way they are to analyze floor vibration and detect activities such as walking or running. If a fall occurs this is also detected.
Also, acoustic sensors can be used for that reason.
c. Camera sensors. These systems are like the others able to detect certain activities of the users' and abnormalities to them.
In contrast to the other sensors, cameras are able to supervise a wide range of activities. Cameras are commonly deployed in a fixed position, which usually raises privacy concerns.
Instead the use of wearable body cameras is also possible. A list with various sensor types and their measurement that are either ambient and in a smart home or wearable and mobile is also given in [13]. Especially wearable sensors are of interest in current AAL applications. Because of their miniaturization they can be integrated seamlessly for example into the clothing of a person and thus enable unobtrusive monitoring. In contrast to other mobile sensors such as in smart phones the sensing here becomes invisible.
By integrating a variety of such miniature sensors on the user's body so called body sensor networks (BSN) can be implemented. Thus, it is possible to asses a holistic health picture of an AAL user [22]. Next to health monitoring, [14] describes fall detection systems and the unobtrusive monitoring of daily activities as important applications of wearable sensors within the AAL domain. The applications of sensors in AAL are also diverse.They can be part of a smart home or be worn directly on the body. In following three projects are presented that use different sensor types to monitor the AAL user.
A. ALMA (Europe): [26] i. targets people with mobility impairments and offers navigation and orientation help.
ii. uses radio frequency emitters for localization of people and objects, also smart cameras for indoor and outdoor localization, environmental monitoring and for assessing situations.

B.
Bioharness (America): [27] i. lightweight wearable system, carried around the chest ii. monitors several physiological parameters such as posture, acceleration or ECG.
iii. offers possibility to view the data live or log it iv. used in an AAL environment to monitor vital parameters.
C. Ubiquitous home (Asia): [28] i. Japanese smart home project ii. monitors the resident by using a variety of sensors iii. passive infrared (PIR) sensors, cameras, microphones, pressure sensors, and radiofrequency identification (RFID).
Sensing is vital for AAL. It monitors the AAL user and provides services based on this data. Sensing is achieved through wearable or static sensors. These can either monitor the person directly or indirect through the environment. Particularly the miniaturization of sensors enables unobtrusive monitoring. Common measurements of these sensors are heartbeat, blood pressure, temperature or falls.

Robotics:
In recent years also the deployment of robotics in the Ambient Assisted Living environment was thematized. These robots can assist in various ways. The applications can range from the assistance with the tasks of daily living to improving the social interactions or provide entertainment. There, [17] gives an overview of the diverse possibilities how robots can be integrated to aid in the life of impaired people. In general, the robots are able to address physical, social or cognitive impairments. In these fields the most common solutions focus on mobility and selfmaintenance for example on feeding, bathing and grooming. These service robots help incapacitated with functional daily activities and thus ensure their independence. Other service robots provide cognitive aid for example by reminding the user to take the correct medicine or to follow a diet. Additional to safety and purposes, some robots are also designed for security and emergency intervention.
They are able to assess risk situations for example when a fall has occurred and then notify a caregiver. Companion robots are researched to improve a patient's wellbeing through humanmachine-interaction. In this way, for example people with a kind of cognitive impairment can be stimulated through the interaction with the robot. The study names another group of robots that provide social, educational or entertainment services.
These group is called interactive simulation robots and focusses on immersive and realistic user experiences. [10] also takes up the importance of companion robots on people with cognitive impairments. They might not cure these impairments but offer stimulation through personal health management, information provision and entertainment. In [22] robots are mentioned as one of the most significant developments inassistive technologies.
Particularly, their ability to monitor and engage people in social activities is stated. Also, [15] describes several projects in Ambient Assisted Living that are using robots. The document mentions for example robots to move objects or presenting food which in general assist functional daily activities. Others can enhance the communication between the person and a caregiver through the robot or improve social activities and entertainment. [14] has reviewed robotic projects in the AAL domain and classified them into several categories based on their assistive focus.
The first category comprises service and companion robots that serve as Electronical Aids to Daily Living (EADLs). These robots can assist with specific tasks such as bathing or serve as reminders for activities such as following a diet. This category also includes cognitive orthotic systems that can help with social interactions.
Further categories include health robots e.g. for managing health data and intelligent physical movement aids.
In contrast to this [13] advocates a different categorization of robots based on the complexity of the task they are assisting with.  As it is stated in [16] the majority of AAL projects focusses on the elderly as the end user, only a minority concerns disabled, children, pregnant women or others. Also, [8] which gives an overview of the current situation in AAL research, describes that the demographic change is a key driver of AAL developments.In Similarly, to the Barthel Index it contains a scoring list to assess a person's independence. This time it includes functional skills necessary to live in a community. The listed activities are more complex than the basic activities of daily living and account for tasks such as using a telephone, shopping, housekeeping and the ability to handle finances [37]. Based on the assessment of these two types of activities the general need for care of a person is determined. In many health care systems these assessments decide over a person's extent of access to health care services and support. This might also decide over the access to Ambient Assisted Living technologies as most people are not able to afford these systems on their own and rely on the national health care system. [32] argues that to enable an independent life at home, the observation of usual and regular activities is not sufficient. Instead, he proposes to assess the cognitive and communicative functions of a person or for example the ability to decide on a daily routine by himself.
This proposal widens the term of care neediness. In this way Ambient Assisted Living products could be accessible for a broader audience. So, could for example companion robots be accessible for people with only mild cognitive impairments. The International Electrotechnical Commission (IEC) has developed several use cases for assisted living technologies and has mapped them to a person's level of need.

i.
On the first level also independent living persons with no need for care are proposed as a potential target group of AAL.
For example, by assisting the self-management of the health status. ii.
On the level where some living assistance is needed the AAL system is supervised by the user. It only occasionally interferes for example in case of a severe emergency.
iii. The next level concerns the instrumental activities of daily living. There, permanent assistance is needed but also the users' interaction.
iv. The highest level of assistance regards the basic activities of daily living. In this case the system should be able to act autonomous. The monitoring of activities then is not enough, active assistance is needed.
This proposal also mainly concerns usual and repeating activities and not directly mentions cognitive or psychological impairments. Still, it states that a deployment of AAL technologies would also be beneficial for people with no impairment for selfmanagement purposes or in emergency situations. Thus, this view goes beyond the general assessment of need for care [38].
In conclusion, the main target group of AAL systems is the elderly end user. In fewer cases the end users were disabled, children or pregnant women. Formal and informal caregivers are not the primary focus of Ambient Assisted Technologies, still they benefit from them indirectly. Nevertheless, AAL devices are not exclusive to a certain user group but depend on the assessment of need for care. This assessment is usually based on the need for help with basic activities of daily living or instrumental activities of daily living. But also, people with the need for communicative or social aid might be users of AAL technologies. Furthermore, the deployment of AAL products for people without any kind of impairment is thinkable for example to increase the acceptance of these technologies once an impairment has occurred.

RQ3 How is the acceptance of Ambient Assisted Living among its end-users?
The wide adoption of AAL systems is highly depended on the acceptancy of these systems by the end-user. This is especially of importance since the target group of AAL consists mostly of seniors. Whereas, systems that are camera-based were refused. People that have already used AAL devices also stated, that they were confused with their operation to some extent.
Further constraints that are hindering a broader deployment of AAL technologies are listed in [22]. They comprise: the lack of skills to use the devices, the uncertainty about its benefits, disabilities that might hinder the intended use and the high costs of some systems. Also, data security is a concern of AAL users. Even though these constraints exist today, [39] states that coming generations will have other technical capabilities and thus, their acceptance of AAL devices might be higher than today. For that reason, still it is necessary to examine how AAL devices need to be designed around the user and which properties are perceived most enjoyable to him.
In [40] the acceptancy of different ambient notification systems has been regarded to asses which systems are least obtrusive and favorable in their users' daily life. There, the projects aim is in general to support the AAL users' daily activities by giving assistance through notifications, e.g. a reminder to drink something. There, warmth as a form of notification was used in a scarf and rated especially high, because it provided a positive feeling. The use of light as a notification to water plants was also rated high, because the light was used in a non-obtrusive way. Auditive signals received less acceptancy because they reminded of alarms. Using ambient sounds such as bird noises as notification was rated higher instead.
[41] presents a study of acceptancy for a user interface that is used in the AAL environment to control several functions of a smart home. The system is a touchscreen PC with an internet connection.
The user interface has been developed together with the future users, which are mainly elderlies. Also, the system was given the human-like name PAUL. Because of the easy to use interface and the humanization of the system it is regarded more as roommate than a technical system. For that reason, also the acceptancy of the connected AAL services is not regarded as obtrusive or watching.
The acceptance of AAL devices is dependent on various factors.
Especially, their subjective perceived use and the price are decisive for the adoption of an AAL device. Older people are in general positive towards AAL, because of a hope for more independence.
Still the willingness to pay is not given. Even though AAL might also ease the life of care givers, informal caregivers are fearing diminishing humaninteraction due to this technology.
Among the mostly elderly end-users particularly security devices were rated positive. As a constraint to the broader adoption of AAL the focus on the mere need for care during the products' development is to mention. Instead a focus on the end-users' perspective should be adopted. The example of PAUL [41] shows that usercentered design makes it possible that the technology can be perceived as non-obtrusive or even human-like. In this way the complexity of AAL devices can be reduced and thus be adopted even by elderly generations with less technical capabilities than future ones.

Threats to Validity
In this paper we aim at giving an overview of three topics

Conclusion
In this paper, we intended to give an overview of the Ambient Assisted Living domain. Therefore, we firstly defined the necessity for the development of AAL solutions. Furthermore, we differentiated the term Ambient Assisted Living from other e-health domains and gave insight into the evolution of AAL devices. To provide an overall picture of the field of AAL the three topics: current applications, end-users and acceptance have been defined as relevant and were investigated in this paper. Regarding these three topics we conclude: i. Various applications exist in the AAL domain to enable independent living in the users' homes. The most common application is the smart home. To provide custom AAL services various sensors are deployed. Also, robots are able to assist the resident in multiple ways.
ii. Due to an ageing society mostly, elderlies are targeted by AAL devices. The devices are also targeted at a specific loss of independence. Next to activities of daily living, AAL assists with social or cognitive impairments. Also, not impaired people might be end-users of AAL iii. The acceptance of AAL among the mostly elderly endusers is mainly positive. The price and the disregarding of user needs during the development are the main hindrance of a broader adoption. A usercentered design is a solution for that.