Academic literature on the topic 'Ambient communication'

The success of the Internet-of-Things (IoT) paradigm relies on, among other things, developing energy-efficient communication techniques that can enable information exchange among billions of battery-operated IoT devices. With its technological capability of simultaneous information and energy transfer, ambient backscatter is quickly emerging as an appealing solution for this communication paradigm, especially for the links with low data rate requirements. However, many challenges and limitations of ambient backscatter have to be overcome for widespread adoption of the technology in future wireless networks. Motivated by this, we study the design and implementation of ambient backscatter systems, including non-coherent detection and encoding schemes, and investigate techniques such as multiple antenna interference cancellation and frequency-shift backscatter to improve the bit error rate performance of the designed ambient backscatter systems. First, the problem of coherent and semi-coherent ambient backscatter is investigated by evaluating the exact bit error rate (BER) of the system. The test statistic used for the signal detection is based on the averaging of energy of the received signal samples. It is important to highlight that the conditional distributions of this test statistic are derived using the central limit theorem (CLT) approximation in the literature. The characterization of the exact conditional distributions of the test statistic as non-central chi-squared random variable for the binary hypothesis testing problem is first handled in our study, which is a key contribution of this particular work. The evaluation of the maximum likelihood (ML) detection threshold is also explored which is found to be intractable. To overcome this, alternate strategies to approximate the ML threshold are proposed. In addition, several insights for system design and implementation are provided both from analytical and numerical standpoints. Second, the highly appealing non-coherent signal detection is explored in the context of ambient backscatter for a time-selective channel. Modeling the time-selective fading as a first-order autoregressive (AR) process, we implement a new detection architecture at the receiver based on the direct averaging of the received signal samples, which departs significantly from the energy averaging-based receivers considered in the literature. For the proposed setup, we characterize the exact asymptotic BER for both single-antenna (SA) and multi-antenna (MA) receivers, and demonstrate the robustness of the new architecture to timing errors. Our results demonstrate that the direct-link (DL) interference from the ambient power source leads to a BER floor in the SA receiver, which the MA receiver can avoid by estimating the angle of arrival (AoA) of the DL. The analysis further quantifies the effect of improved angular resolution on the BER as a function of the number of receive antennas. Third, the advantages of utilizing Manchester encoding for the data transmission in the context of non-coherent ambient backscatter have been explored. Specifically, encoding is shown to simplify the detection procedure at the receiver since the optimal decision rule is found to be independent of the system parameters. Through extensive numerical results, it is further shown that a backscatter system with Manchester encoding can achieve a signal-to-noise ratio (SNR) gain compared to the commonly used uncoded direct on-off keying (OOK) modulation, when used in conjunction with a multi-antenna receiver employing the direct-link cancellation. Fourth, the BER performance of frequency-shift ambient backscatter, which achieves the self-interference mitigation by spatially separating the reflected backscatter signal from the impending source signal, is investigated. The performance of the system is evaluated for a non-coherent receiver under slow fading in two different network setups: 1) a single interfering link coming from the ambient transmission occurring in the shifted frequency region, and 2) a large-scale network with multiple interfering signals coming from the backscatter nodes and ambient source devices transmitting in the band of interest. Modeling the interfering devices as a two dimensional Poisson point process (PPP), tools from stochastic geometry are utilized to evaluate the bit error rate for the large-scale network setup.<br>Doctor of Philosophy<br>The emerging paradigm of Internet-of-Things (IoT) has the capability of radically transforming the human experience. At the heart of this technology are the smart edge devices that will monitor everyday physical processes, communicate regularly with the other nodes in the network chain, and automatically take appropriate actions when necessary. Naturally, many challenges need to be tackled in order to realize the true potential of this technology. Most relevant to this dissertation are the problems of powering potentially billions of such devices and enabling low-power communication among them. Ambient backscatter has emerged as a useful technology to handle the aforementioned challenges of the IoT networks due to its capability to support the simultaneous transfer of information and energy. This technology allows devices to harvest energy from the ambient signals in the environment thereby making them self-sustainable, and in addition provide carrier signals for information exchange. Using these attributes of ambient backscatter, the devices can operate at very low power which is an important feature when considering the reliability requirements of the IoT networks. That said, the ambient backscatter technology needs to overcome many challenges before its widespread adoption in IoT networks. For example, the range of backscatter is limited in comparison to the conventional communication systems due to self-interference from the power source at a receiver. In addition, the probability of detecting the data in error at the receiver, characterized by the bit error rate (BER) metric, in the presence of wireless multipath is generally poor in ambient backscatter due to double path loss and fading effects observed for the backscatter link. Inspired by this, the aim of this dissertation is to come up with new architecture designs for the transmitter and receiver devices that can improve the BER performance. The key contributions of the dissertation include the analytical derivations of BER which provide insights on the system design and the main parameters impacting the system performance. The exact design of the optimal detection technique for a communication system is dependent on the channel behavior, mainly the time-varying nature in the case of a flat fading channel. Depending on the mobility of devices and scatterers present in the wireless channel, it can either be described as time-selective or time-nonselective. In the time-nonselective channels, coherent detection that requires channel state information (CSI) estimation using pilot signals can be implemented for ambient backscatter. On the other hand, non-coherent detection is preferred when the channel is time-selective since the CSI estimation is not feasible in such scenarios. In the first part of this dissertation, we analyze the performance of ambient backscatter in a point-to-point single-link system for both time-nonselective and time-selective channels. In particular, we determine the BER performance of coherent and non-coherent detection techniques for ambient backscatter systems in this line of work. In addition, we investigate the possibility of improving the BER performance using multi-antenna and coding techniques. Our analyses demonstrate that the use of multi-antenna and coding can result in tremendous improvement of the performance and simplification of the detection procedure, respectively. In the second part of the dissertation, we study the performance of ambient backscatter in a large-scale network and compare it to that of the point-to-point single-link system. By leveraging tools from stochastic geometry, we analytically characterize the BER performance of ambient backscatter in a field of interfering devices modeled as a Poisson point process.

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e de Computadores<br>The society that we live in faces today big demographic changes. Nowadays, peo-ple live longer, and it is expected that this trend will proceed. In 2000, there were already 420 million people with more than 65 years old, which correspond to about 7% of the world population. In 2050, it is expected that this number reaches 1500 million which corresponds to about 16% of the world population. Naturally, in these circumstances, the number of disabled people will increase as well. This context brings new challenges to the traditional health care systems in Portugal and in the rest of the world. There is an urgent need to search for new solutions that will allow people to live in the best possible way, in the latest stages of life. In order to fulfill this need, it is necessary to develop systems that allow to extend their life in their favorite environment, improving their safety, autonomy, mobility and welfare. Nowadays, information and communication technologies (ICT) offer new opportunities to provide care and assistance. Ambient Assisted Living (AAL), is such a paradigm, in which technology is used as a way to improve the independ-ence and welfare of aged or disabled people at their homes. This dissertation has the purpose of contributing to providing an answer to this necessity, associated to a development of an ecosystem for Ambient Assisted Living, associated to a business model and the search for the possibility of collabo-rative networks creation, in order to look for efficient and accessible solutions for AAL services provision.

Vatten är en livsviktig resurs vars tillgång på senare tid varit begränsad. År 2019 hade 15 av 21 län i Sverige risk för vattenbrist. KTH samarbetar med företaget Ecoloop som driver ett utvecklingsprojekt med målet att utveckla strategier för vattenbesparing och beteendeförändring som resulterar i minskad vattenanvändning. Visualisering av vattenförbrukning pekas ut som en möjlig strategi för att stödja beteendeförändring. Med utgångspunkt i Ecoloops besparingsmål undersökte vi hur ett visualiseringsverktyg kan representera vattenförbrukning och hur detta kan påverka människors motivation att förändra sitt beteende kring vattenkonsumtion. Tidigare forskning visar att ett ambient verktyg (som existerar i omgivningen som en subtil påminnelse) är lämpligt för att uppmuntra till beteendeförändring då det är ett sätt att öka medvetenhet utan påträngande återkoppling. Vi utvecklade en ambient prototyp av en väggkalender för att visualisera hushålls vattenkonsumtion. Undersökningen av prototypens potential genomfördes i två steg. Först utfördes användartester på en pappersprototyp för att utvärdera användarnas förståelse. Utifrån det togs en digital prototyp fram, vars motivation till beteendeförändring utvärderades genom kvalitativa intervjuer med målgruppen. Målgruppen, mer specifikt, var individer som nyligen flyttat hemifrån. Denna grupp är av stor relevans då de befinner sig i en situation där de för första gången själva får bestämma över sitt hushåll och beteenden. Användartesternas resultat visar att prototypen är ett bra hjälpmedel för att användaren ska få god förståelse för sin vattenkonsumtion. Då det är ett visualiseringsverktyg som är integrerat i vardagen visade resultaten att prototypen har god potential till att påverka motivation till förändrat beteende genom att ge återkoppling som är upplysande och närvarande snarare än påträngande. Användarna i de utförda testerna uttryckte att de var motiverade av prototypen då den ger snabb och intuitiv återkoppling vattenkonsumtionen. Främst uppskattades kombinationen av den symboliska återkopplingen i kombination med de faktiska mätningarna. Våra slutsatser visar att prototypen har potential att leda till beteendeförändring, men det går inte att säga någonting kring om det faktiskt hade lett till en väsentligt minskad vattenanvändning.<br>Water is a vital resource whose supply has recently been limited. In 2019, 15 out of 21 counties in Sweden were at risk of water shortages. KTH has a collaboration with the company Ecoloop, which runs a development project with a goal of developing strategies for water saving and behavior change that results in reduced water use. Visualization of water consumption is pointed out as a possible strategy to support behavior change. Based on Ecoloop's saving goals, this report examines how a visualization tool can represent water consumption and how this can affect people's motivation to change their behavior regarding their water consumption. Previous research shows that an ambient display (which exists in the environment as a subtle reminder) is suitable for encouraging behavior change as it is a way to create awareness without intrusive feedback. After an understanding of water consumption challenges in Sweden were formed, a prototype of a wall calendar was developed to visualize household water consumption. The study of the prototypes potential was conducted in two stages. First, user tests were performed on a paper prototype to evaluate comprehension. Based on this, a digital prototype was developed. Secondly, qualitative interviews were conducted to evaluate the target group’s motivation for behaviour change. The target group, more specifically, were individuals who had recently moved from their childhood homes. This group is of great importance because they are in a situation where they for the first time are in charge of their own household and behavior. The results show that our prototype is a good tool for the user to gain understanding of their water consumption. As it is a visualization tool that is integrated into everyday life, the results showed that the prototype has good potential to influence motivation for behaviour change by providing feedback that is enlightening and attendant rather than intrusive. The users expressed that they were motivated by the prototype as it provides fast and intuitive feedback of their water consumption. Mainly appreciated was the symbolic feedback in combination with the actual measurements. Our conclusions show that the prototype has potential to lead to behaviour change, but it is not possible to say anything about whether our display actually would have led to a significant reduction in water usage.

Loneliness is a growing social problem that affects people from different age groups. Studies have shown that loneliness is prevalent more in young adults and the elderly demographic. Loneliness can pose serious health issues like cognitive malfunction, heart disease, stroke, depression, etc. People who stay alone from friends and family tend to feel lonelier. Conventional communication tools like a phone or video calls or using social media applications can help the users connect with people but also have adverse effects. As a result of this, the potential of an alternative nonverbal mode of communication needs to be explored. The research aims to understand individuals' behavior, traits, and hidden needs when it comes to loneliness. The purpose is to suggest an alternative way of communication that creates a sense of presence and ensures mental well for the people living alone and suffer from emotional loneliness. The concept of Calm and ambient technology has been explored in this thesis as an alternative means of communication. Users’ needs were gathered from eight semi-structured interviews, and two stakeholders were identified. Over forty ideas were generated from brainstorming. The ideas were sent to twenty individuals through snowballing. The response from them was analyzed and narrowed down by using concept screening and concept scoring. The final concept was a device called ‘One home lamp.’ The device uses light to show the presence of remote family members or loved ones to a person living alone. This concept product was then evaluated through ‘Mankoff’s heuristics’ to see its credibility as a calm ambient artifact.

Background noise is ubiquitous and can impair acoustic communication and influence signaling behavior in animals. Despite evidence demonstrating myriad effects of anthropogenic noise on animal communication, precisely how natural background noise influences communication and behavior remains unclear. Yet, natural sources of background noise, such as rushing rivers or crashing ocean surf, share similar power spectra to sources of anthropogenic noise and can occur at high amplitudes, potentially masking acoustic signals. To investigate the effects of water-generated noise on songbird behavior, we experimentally broadcast landscape-level playbacks of ocean surf and river noise in coastal California, USA, and riparian habitat in Idaho, USA, respectively. In Chapter 1, we conducted a conspecific playback experiment examining how territorial defense behaviors of lazuli buntings (Passerina amoena) and spotted towhees (Pipilo maculatus) vary in response to broadcast water noise. We also incorporated cicada noise from a serendipitous Okanagana spp. emergence as a biotic source influencing lazuli bunting behavior. Both species produce songs that share substantial spectral overlap with low-frequency, water-generated noise, and lazuli bunting song shares an additional high-frequency overlap with cicada calls. Thus, there is potential for background acoustic conditions to mask conspecific signals. We found that detection and discrimination of conspecific playback occurred more slowly for both species as sound level increased. Lazuli buntings also exhibited divergent flight behaviors in response to high- and low-frequency acoustic sources, both dependent and independent of sound level. In Chapter 2, we investigated how amplitude and frequency of water-generated noise influences spectral and temporal song characteristics in six songbird species. We recorded individuals defending territories across 37 sites, with each site representing one of four acoustic environments: naturally quiet ‘controls’, naturally noisy ‘positive controls’ adjacent to the ocean or a whitewater river, ‘phantom’ playback sites with continuous broadcast of low-frequency water noise, and ‘shifted’ playback sites with continuous broadcast of high-frequency water noise. We predicted that all individuals exposed to ‘positive control’, ‘phantom’, or ‘shifted’ noise would adjust song structure, but the magnitude of signal modification would be larger in noisier locations and the type of modification would depend on the spectral profile of the acoustic environment. No two species altered songs in precisely the same way. However, song structure of all six species varied with amplitude and/or frequency of background noise. Together our results demonstrate that natural noise can impair agonistic behaviors and influence vocal structure. These findings suggest that the natural acoustic environment shapes acoustic communication, highlighting natural soundscapes as an under-appreciated axis of the environment.

La qualité des données est une condition commune à tous les projets de technologie de l'information, elle est devenue un domaine de recherche complexe avec la multiplicité et l’expansion des différentes sources de données. Des chercheurs se sont penchés sur l’axe de la modélisation et l’évaluation des données, plusieurs approches ont été proposées mais elles étaient limitées à un domaine d’utilisation bien précis et n’offraient pas un profil de qualité nous permettant d’évaluer un modèle de qualité de données global. L’évaluation basée sur les modèles de qualité ISO a fait son apparition, néanmoins ces modèles ne nous guident pas pour leurs utilisation, le fait de devoir les adapter à chaque cas de figure sans avoir de méthodes précises. Notre travail se focalise sur les problèmes de la qualité des données d'un système ambiant où les contraintes de temps pour la prise de décision sont plus importantes par rapport aux applications traditionnelles. L'objectif principal est de fournir au système décisionnel une vision très spécifique de la qualité des données issues des capteurs. Nous identifions les aspects quantifiables des données capteurs pour les relier aux métriques appropriées de notre modèle de qualité de données spécifique. Notre travail présente les contributions suivantes : (i) création d’un modèle de qualité de données générique basé sur plusieurs standards de qualité existants, (ii) formalisation du modèle de qualité sous forme d’une ontologie qui nous permet l’intégration de ces modèles (de i), en spécifiant les différents liens, appelés relations d'équivalence, qui existent entre les critères composant ces modèles, (iii) proposition d’un algorithme d’instanciation pour extraire le modèle de qualité de données spécifique à partir du modèle de qualité de données générique, (iv) proposition d’une approche d’évaluation globale du modèle de qualité de données spécifique en utilisant deux processus, le premier processus consiste à exécuter les métriques reliées aux données capteurs et le deuxième processus récupère le résultat de cette exécution et utilise le principe de la logique floue pour l’évaluation des facteurs de qualité de notre modèle de qualité de données spécifique. Puis, l'expert établie des valeurs représentant le poids de chaque facteur en se basant sur la table d'interdépendance pour prendre en compte l'interaction entre les différents critères de données et on utilisera la procédure d'agrégation pour obtenir un degré de confiance. En ce basant sur ce résultat final, le composant décisionnel fera une analyse puis prendra une décision<br>Data quality is a common condition to all information technology projects; it has become a complex research domain with the multiplicity and expansion of different data sources. Researchers have studied the axis of modeling and evaluating data, several approaches have been proposed but they are limited to a specific use field and did not offer a quality profile enabling us to evaluate a global quality model. The evaluation based on ISO quality models has emerged; however, these models do not guide us for their use, having to adapt them to each scenario without precise methods. Our work focuses on the data quality issues of an ambient system where the time constraints for decision-making is greater compared to traditional applications. The main objective is to provide the decision-making system with a very specific view of the sensors data quality. We identify the quantifiable aspects of sensors data to link them to the appropriate metrics of our specified data quality model. Our work presents the following contributions: (i) creating a generic data quality model based on several existing data quality standards, (ii) formalizing the data quality models under an ontology, which allows integrating them (of i) by specifying various links, named equivalence relations between the criteria composing these models, (iii) proposing an instantiation algorithm to extract the specified data quality model from the generic data quality models, (iv) proposing a global evaluation approach of the specified data quality model using two processes, the first one consists in executing the metrics based on sensors data and the second one recovers the result of the first process and uses the concept of fuzzy logic to evaluate the factors of our specified data quality model. Then, the expert defines weight values based on the interdependence table of the model to take account the interaction between criteria and use the aggregation procedure to get a degree of confidence value. Based on the final result, the decisional component makes an analysis to make a decision

Federal regulations specify that an employee working for eight hours cannot legally be exposed to noise which has a time-weighted average greater than 90 decibels on the A scale. The industrial workforce is comprised of not only people with normal hearing acuity, but of individuals who suffer from hearing loss. While current noise regulation standards are deemed appropriate for those with normal hearing, it is difficult to apply these standards to persons wearing hearing aids on the job. The ambient, or unamplified, noise levels that fall below the maximum permitted by OSHA standards may very well be amplified to levels greater than 90 dBA, by the hearing aid. If this were the case, the company employing the hearing aid user would technically be in violation of the OSHA regulations. This study addressed the question of what noise exposure might be expected for hearing aid users on the job in different situations, as well as in non-vocational settings. The research involved two methods, conducted to determine the noise levels created by hearing aids with different amounts of gain and to determine whether the amplified noise levels exceed those requiring intervention under current regulations. For both methods, ambient and amplified noise levels for each condition were gathered in specified increments, and were compared with regard to current regulatory standards. The resultant data revealed that when ambient noise levels average between 80 and 84 dBA, amplification provided by even a mild gain hearing aid caused the eight hour time-weighted averages (TWA's) to increase to levels above the 90 dBA maximum permissible levels as delineated by OSHA. Moderate and high gain aids further increased these levels. The results of this study suggest that the hearing aid users in industrial and perhaps non-industrial settings may very well be exposed to intensity levels which exceed OSHA maximums, even when ambient levels do not. The extent to which these arc exceeded are based on the gain and output of the hearing aid in use.