Impact of packet loss on the perceived quality of UDP-based multimedia streaming: a study of user quality of experience in real-life environments

Multimedia content delivery has become one of the pillar services of modern day mobile and fixed networks. The variety of devices, platforms, and content providers together with increasing network capacity has impacted the popularity of this type of service. Considering this context, it is crucial to ensure end-to-end service quality that can fulfill users’ expectations. The user quality of experience (QoE) for multimedia streaming is tempered by numerous objective and subjective parameters; therefore, it is important to understand the relationships among them. In this paper, we thoroughly examine the impact of packet loss on user QoE in cases when multimedia streaming service is based on underlying User Datagram Protocol. The dependencies between the chosen objective and subjective parameters and the user QoE were examined in a real-life environment by conducting a survey with 602 test subjects who rated the quality of a 1-h documentary film (72 different test sequences were prepared for the rating process). Based on the obtained results, we ranked the objective parameters by their order of importance in relation to their impact on user QoE as follows: (1) total duration of packet loss occurrences (PLOs), i.e., quality distortions in a video; (2) number of PLOs; (3) packet loss rate; and (4) duration of a single PLO. We also demonstrated how the overall user experience can be redeemed, despite the perceived quality distortions, if the content is entertaining to the viewer. The user experience was also found to be influenced by the existence/non-existence of video subtitles.     

Actual vs. perceived effect of software engineering practices in the Italian industry

A commonly cited limitation of software engineering research consists in its detachment from the industrial practice. Several studies have analyzed a number of practices and identified their benefits and drawbacks but little is known about their dissemination in the industry. For a set of 18 practices commonly studied in the literature, this paper investigated diffusion, effect on the success, and perceived usefulness in 62 actual industrial projects from 28 Italian IT companies. In particular we proposed a classification of these perceptions and we were able to classify 14 practices. We found statistical evidence that 7 factors have an actual effect (positive for 6 of them, negative for one). Moreover 77% (10 out of 13) of the known good practices (e.g., importance of good project schedule or complete requirements’ list) are perceived consistently by the industry. For a few other practices (having a champion's support, using metrics, reducing quality) we noticed a lack of awareness in the industry. Starting from these observations we propose guidelines for industrial practice and suggestions for academic research.     

Expected user experience of mobile augmented reality services: a user study in the context of shopping centres

The technical enablers for mobile augmented reality (MAR) are becoming robust enough to allow the development of MAR services that are truly valuable for consumers. Such services would provide a novel interface to the ubiquitous digital information in the physical world, hence serving in great variety of contexts and everyday human activities. To ensure the acceptance and success of future MAR services, their development should be based on knowledge about potential end users’ expectations and requirements. We conducted 16 semi-structured interview sessions with 28 participants in shopping centres, which can be considered as a fruitful context for MAR services. We aimed to elicit new knowledge about (1) the characteristics of the expected user experience and (2) central user requirements related to MAR in such a context. From a pragmatic viewpoint, the participants expected MAR services to catalyse their sense of efficiency, empower them with novel context-sensitive and proactive functionalities and raise their awareness of the information related to their surroundings with an intuitive interface. Emotionally, MAR services were expected to offer stimulating and pleasant experiences, such as playfulness, inspiration, liveliness, collectivity and surprise. The user experience categories and user requirements that were identified can serve as targets for the design of user experience of future MAR services.     

Printing and screen reading in the medical school curriculum: Guttenberg vs. the cathode ray tube

Abstract

Functions which control access to data in groupware should be designed flexibly by offering different options to end users. However, conflicts might arise among different end users in the process of selecting one of these options. To support users in finding a consensual solution for these conflicts, we propose a metafunction called ‘negotiability’. We propose to define and explore the concept of ‘negotiability’, and discuss its application to access control, concurrency control, and consistency control. We assume that negotiability can play an important role in tailoring these mechanisms and supporting a co-operative use of system's flexibility.     

Printing and screen reading in the medical school curriculum: Guttenberg vs. the cathode ray tube

Integrating computer-based learning into the medical school curriculum is hampered by students' propensity to print all digitally available material. The research presented here examines print vs. on-screen consumption of information. In interviews with medical school students variables?Time/Convenience Issues; Habituated Learning Styles and Document Formatting?emerged as patterns repeated by five or more subjects when asked 'why do you print instead of reading material on the screen?' These variables suggest there may be both hardware and software applications that could enhance the utility of student laptops. For example, less cumbersome computers with software allowing simultaneous multi-document use and annotating might be valuable features for students. Several variables, however, are outside the control of academic computing; for example, habituated learning from print and student time constraints. These findings provide a foundation to develop hardware and software design that would encourage on-screen use of information.     

Understanding the impact of perceived visual aesthetics on user evaluations: An emotional perspective

Studies aimed at predicting user judgments have been dominated by the usability and efficiency perspective. An important assumption of this perspective is that higher order judgments such as quality perception and download intention are mainly cognitive processes. Increasingly, research has shown that this perspective is incapable of fully explaining user judgments. Emerging research posits that emotions and emotional subcomponents that arise from aesthetic-based design factors are at least equally important for understanding how users form higher order judgments such as quality perception and attractiveness. In this article, light is shed on the role of emotions in affecting these judgments. This is performed for the particular case of mobile apps. Specifically, the relationship between various aesthetic subdimensions (classical and expressive) and emotional subcomponents (valence and arousal) is explored. First, an explanatory model from theories of aesthetics, emotions, and visual perception is derived. Second, a laboratory experiment is conducted, and it provides empirical evidence for the relationships between visual aesthetics, emotions, and higher order evaluations such as users' quality perceptions and the intentions to download. Specifically, significant relationships were found between aesthetic subdimensions and valence, whereas arousal was partially significant. Selective emotional subdimensions also significantly impacted quality perceptions, attractiveness, and intention to download. Finally, implications for theory and practice are discussed.     

HMD versus PDA: a comparative study of the user out-of-box experience

The out-of-box experience (OOBE) has been identified as a significant factor contributing to user perception and acceptance of products and technologies. Whilst there has been considerable emphasis placed on formalising methodological procedures for evaluating the OOBE and on the creation of positive user experiences through appropriate interfaces and applications, relatively little work has been undertaken examining how the OOBE is impacted when the experience itself covers a range of (possibly interconnected) devices. In this paper we report the results of an empirical study which examined the OOBE when a Personal Digital Assistant (PDA) and Head Mounted Device (HMD) were configured and then connected for inter-operability purposes. Our findings show that type of device has a considerable impact on the OOBE, with the ask of interconnecting devices having a detrimental effect on the OOBE. The OOBE, however, is in main unaffected by user type and gender.     

Investigating the affective quality of interactivity by motion feedback in mobile touchscreen user interfaces

Emotion is a key aspect of user experience. To design a user interface for positive emotional experience, the affective quality of the user interface needs to be carefully considered. A major factor of affective quality in today's user interface for digital media is interactivity, in which motion feedback plays a significant role as an element. This role of motion feedback is particularly evident in touchscreen user interfaces that have been adopted rapidly in mobile devices. This paper presents two empirical studies performed to increase our understanding of motion feedback in terms of affective quality in mobile touchscreen user interfaces. In the first study, the relationships between three general motion properties and a selected set of affective qualities are examined. The results of this study provide a guideline for the design of motion feedback in existing mobile touchscreen user interfaces. The second study explores a new dimension of interactivity that is the Weight factor of Laban's Effort system. To experiment the Weight factor in a mobile touchscreen user interface, a pressure sensitive prototype was developed to recognize the amount of force applied by the user's finger action. With this prototype, the effects of implementing pressure requirements on four different types of user interfaces were examined. Results show that implementing the Weight factor can significantly influence the affective quality and complement the physical feel of a user interface. The issues to consider for effective implementation are also discussed.     

Control of perceived quality of service in multimedia retrieval services: prediction-based mechanism vs. compensation buffers

In multimedia systems end-to-end delay jitter has a great impact on the continuity of information playback. Therefore, it is necessary to introduce appropriate mechanisms to compensate for delay variations, so that the intramedia and intermedia temporal relationships can be preserved. In this paper, two methods for compensation of the network delay jitter in a distributed multimedia retrieval service are compared: the first is based on prediction of the network delay jitter suffered by each information unit and retrieval time modification at the source site; the second is based on a compensation buffer at the destination site. Comparison is made by assuming a master/slave relationship between the monomedia streams composing the multimedia data flow.     

Icon identification in context: the changing role of icon characteristics with user experience

OBJECTIVE: This research examined the relative importance of icon characteristics in determining the speed and accuracy of icon identification. BACKGROUND: Studies to date have focused on the role of one or two icon characteristics when users first experience an icon set. This means that little is known about the relative importance of icon characteristics or how the role of icon characteristics might change as users gain experience with icons. METHODS: Thirty participants carried out an icon identification task over a long series of trials to simulate learning through experience. Icon characteristics investigated included semantic distance, concreteness, familiarity, and visual complexity. RESULTS: Icon characteristics were major determinants of performance, accounting for up to 69% of the variance observed in performance. However, the importance of icon characteristics changed with experience: Semantic distance is crucial initially while icon-function relationships are learned, but familiarity is important later because it has lasting effects on access to long-term memory representations. CONCLUSION: These findings suggest that icon concreteness may not be of primary importance when identifying icons and that semantic distance and familiarity may be more important. APPLICATION: Designers need to take into account icon characteristics other than concreteness when creating icons, particularly semantic distance and familiarity. The precise importance of the latter characteristics will vary depending on whether icons are rarely encountered or frequently used.     

The influence of design aesthetics in usability testing: Effects on user performance and perceived usability

This article examined the effects of product aesthetics on several outcome variables in usability tests. Employing a computer simulation of a mobile phone, 60 adolescents (14-17 yrs) were asked to complete a number of typical tasks of mobile phone users. Two functionally identical mobile phones were manipulated with regard to their visual appearance (highly appealing vs not appealing) to determine the influence of appearance on perceived usability, performance measures and perceived attractiveness. The results showed that participants using the highly appealing phone rated their appliance as being more usable than participants operating the unappealing model. Furthermore, the visual appearance of the phone had a positive effect on performance, leading to reduced task completion times for the attractive model. The study discusses the implications for the use of adolescents in ergonomic research.     

Exploring the wiki user experience: The effects of training spaces on novice user usability and anxiety towards wiki editing

With the advent of Web 2.0, the number of IT systems used in university courses is growing. Yet research consistently shows that a significant proportion of students are anxious about computer use. The quality of first experience with computers has been consistently mentioned as a significant contributor to anxiety onset. However the effect of users’ first experience on system related anxiety has not to the authors’ knowledge been researched using controlled experiments. Indeed little experiment based research has been conducted on the wiki user experience, specifically users’ evaluations and emotional reactions towards editing. This research uses usability engineering principles to engineer four different wiki experiences for novice wiki users and measures the effect each has on usability, anxiety during editing and on anxiety about future wiki editing. Each experience varied in the type of training spaces available before completing six live wiki editing tasks. We found that anxiety experienced by users was not related to computer anxiety but was wiki specific. Users in the in-built tutorial conditions also rated the usability of the editing interface higher than users in the non-tutorial conditions. The tutorial conditions also led to a significant reduction in wiki anxiety during interaction but did not significantly affect future editing anxiety. The findings suggest that the use of an in-built tutorial reduces emotional and technological barriers to wiki editing and that controlled experiments can help in discovering how aspects of the system experience can be designed to affect usability and anxiety towards editing wikis.     

A cross-cultural comparison of perceived hazard in response to warning components and configurations: US vs. China

There is increasing momentum towards international harmonization of warning standards. Therefore, it is critical to determine the applicability of existing standards across different cultures. Perceived hazard in response to isolated warning components (colors, signal words and symbols) and warning configurations was examined as a function of culture of the product-user (US vs. China) to determine the extent to which ANSI (American National Standards Institute)-recommended components/configurations communicate the expected level of hazard across cultures. 40 college students in the US and 43 in China rated colors, signal words, symbols, and complex configurations on a scale from 1 (not at all hazardous) to 9 (extremely hazardous). US participants consistently provided higher ratings of perceived hazard than Chinese participants. Cross-cultural differences were also observed in the relative levels of perceived hazard assigned to different levels of a label component, particularly in response to colors. However, relative levels of perceived hazard among more complex configurations were similar across culture, even though Chinese participants continued to provide lower absolute ratings of perceived hazard. These results have important implications - if it is assumed that perceived hazard-level must attain some threshold value in order to trigger compliance, then differences in perception could result in a failure of product-users to take appropriate precautions.     

Performance comparison of neural network models: backpropagation vs. fuzzy artmap

Neural networks have been increasingly applied to many problems in civil engineering. Even though there are currently many different types of neural network models, Backpropagation is the most popular neural network model. It is also known that Fuzzy ARTMAP, which is a combination of fuzzy logic and Adaptive Resonance Theory (ART), is superior to any other neural network models in terms of computing cost and predictive accuracy. In this research, two neural network paradigms, Backpropagation and Fuzzy ARTMAP have been studied to compare their performance in terms of computing cost and predictive accuracy through the experiment with real world image data of traffic scenes, as well as biological and theoretical aspects. In addition, three enhanced Backpropagation models, Backpropagation with Momentum, Quickprop, BPMP (Backpropagation with Momentum and Prime-offset) have been considered to compare the network performance of each model.     

Performance analysis of dynamic finite versioning schemes: storagecost vs. obsolescence

Dynamic finite versioning (DFV) schemes are an effective approach to concurrent transaction and query processing, where a finite number of consistent, but maybe slightly out-of-date, logical snapshots of the database can be dynamically derived for query access. In DFV, the storage overhead for keeping additional versions of changed data to support the logical snapshots and the amount of obsolescence faced by queries are two major performance issues. We analyze the performance of DFV, with emphasis on the trade-offs between the storage cost and obsolescence. We develop analytical models based on a renewal process approximation to evaluate the performance of DFV using M⩾2 snapshots. Asymptotic closed form results for high query arrival rates are given for the case of two snapshots. Simulation is used to validate the analytical models and to evaluate the tradeoffs between various strategies for advancing snapshots when M>2. The results show that (1) the analytical models match closely with simulation; (2) storage cost and obsolescence are sensitive to the snapshot advancing strategies, and (3) usually, increasing the number of snapshots demonstrates a trade-off between storage overhead and query obsolescence. For cases with skewed accessor low update rates, a small increase in the number of snapshots beyond two can substantially reduce the obsolescence. Such a reduction in obsolescence is more significant as the coefficient of variation of the query length distribution becomes larger. Moreover, for very low update rates, a large number of snapshots can be used to reduce the obsolescence to almost zero without increasing the storage overhead     

Performance evaluation of user applications in the ITS scenario: An analytical assessment of the NeMHIP

Internet connectivity in the ITS context is a flourishing demand that has to be covered by efficient information and communication technologies. Thanks to the provision of this connectivity, not only end users will profit from communication services, but also services for controlling the operation of the vehicle will benefit from the Internet connectivity. Services related to the operation and control of the vehicles exchange sensitive data, so strong security properties have to be ensured for this type of services. In addition, because of the privacy concerns related to the end users, it is desired to provide this kind of services with an adequate security level. From the communication point of view, a vehicle can be regarded as a mobile network where nodes onboard obtain continuous and optimal Internet connectivity, so, its mobility has to be managed. In the same way, network mobility management protocols should not only avoid security leaks, but also they have to ensure an adequate security level. It is needless to say that the introduction of security properties cannot render not fulfilling service performance requirements. In fact, the trade-off between security and application performance is a must. ITS standardisation bodies have adopted the NEtwork MObility Basic Support (NEMO BS) protocol to manage the mobility of networks. However, it still presents shortcomings like lack of security support and routing problems, which leads to a bad performance. One of the most promising design approaches is to consider a base mobility management protocol that provides out of the box security and route optimisation support like the Host Identity Protocol (HIP). Different solutions based on HIP can be found to solve network mobility in the literature, but none of these solutions aim at solving securely and efficiently network mobility management. That is, the provision of security properties to the network mobility management itself and to the end-to-end data communications while not increasing the signalling overhead and the manageability level remains unsolved. In this paper, we present the NeMHIP. NeMHIP is a secure and efficient network mobility management protocol which is based on HIP. In order to demonstrate its feasibility, we have carried out a study by means of analytical modelling to assess the performance of user applications with stringent QoS requirements like VoIP. Results demonstrate that the introduction of the NeMHIP in the ITS context is feasible because security properties are ensured while application performance requirements are satisfied. Therefore, we successfully achieve the trade-off between security and performance.     

Appropriate and inappropriate legal protection of user interfacesand screen displays. 3. Copyright law, the courts, and the copyrightoffice

For pt.2 see ibid., vol.9, no.4, p.7-10, 92-4 (1989). The applicability of US copyright laws to computer programs is examined, and the enforcement of copyrights is discussed. Court decisions are cited showing that the copyright status of screen displays for computer programs remains confused. An important variable in predicting the scope of copyright protection, namely, the position that the US Copyright Office takes in the exercise of its registration function and in its rulemaking capacity, is examined     

Page flipping vs. clicking: The impact of naturally mapped interaction technique on user learning and attitudes

Newer interaction techniques enable users to explore interfaces in a more natural and intuitive way. However, we do not yet have a scientific understanding of their contribution to user experience and theoretical mechanisms underlying the impact. This study examines how a naturally mapped interface, page-flipping interface, can influence user learning and attitudes. An online experiment with two conditions (page flipping vs. clicking) tests the impact of this naturally mapped interaction technique on user learning and attitudes. The result shows that the page-flipping feature creates more positive evaluations of the website in terms of usability and engagement, as well as greater behavioral intention towards the website by evoking greater perception of natural mapping and greater feeling of presence. In terms of learning outcomes, however, participants who flip through the online magazine show less recall and recognition memory, unless they perceive page flipping as more natural and intuitive to interact with. Participants perceive the same content as more credible when they flip through the content, but only if they appreciate the coolness of the medium. Theoretical and practical implications will be discussed.     

Predictors of user perceptions of web recommender systems: How the basis for generating experience and search product recommendations affects user responses

One critical question suggested by Web 2.0 is as follows: When is it better to leverage the knowledge of other users vs. rely on the product characteristic-based metrics for online product recommenders? Three recent and notable changes of recommender systems have been as follows: (1) a shift from characteristic-based recommendation algorithms to social-based recommendation algorithms; (2) an increase in the number of dimensions on which algorithms are based; and (3) availability of products that cannot be examined for quality before purchase. The combination of these elements is affecting users’ perceptions and attitudes regarding recommender systems and the products recommended by them, but the psychological effects of these trends remain unexplored. The current study empirically examines the effects of these elements, using a 2 (recommendation approach: content-based vs. collaborative-based, within)×2 (dimensions used to generate recommendations: 6 vs. 30, between)×2 (product type: experience products (fragrances) vs. search products (rugs), between) Web-based study (N=80). Participants were told that they would use two recommender systems distinguished by recommendation approach (in fact, the recommendations were identical). There were no substantive main effects, but all three variables exhibited two-way interactions, indicating that design strategies must be grounded in a multi-dimensional understanding of these variables. The implications of this research for the psychology and design of recommender systems are presented.