Progressive image transmission over differentially space‐time coded OFDM systems

In this paper, we consider progressive image transmission over differentially space‐time coded orthogonal frequency‐division multiplexing (OFDM) systems and treat the problem as one of optimal joint source‐channel coding (JSCC) in the form of unequal error protection (UEP), as necessitated by embedded source coding (e.g., SPIHT and JPEG 2000). We adopt a product channel code structure that is proven to provide powerful error protection and employ low‐complexity decision‐feedback decoding for differentially space‐time coded OFDM without assuming channel state information. For a given SNR, the BER performance of the differentially space‐time coded OFDM system is treated as the channel condition in the JSCC/UEP design via a fast product code optimization algorithm so that the end‐to‐end quality of reconstructed images is optimized in the average minimum MSE sense. Extensive image transmission experiments show that SNR/BER improvements can be translated into quality gains in reconstructed images. Moreover, compared to another non‐coherent detection algorithm, i.e., the iterative receiver based on expectation‐maximization algorithm for the space‐time coded OFDM systems, differentially space‐time coded OFDM systems suffer some quality loss in reconstructed images. With the efficiency and simplicity of decision‐feedback differential decoding, differentially space‐time coded OFDM is thus a feasible modulation scheme for applications such as wireless image over mobile devices (e.g., cell phones). Copyright © 2006 John Wiley & Sons, Ltd.     

Parallel Repetition of Computationally Sound Protocols Revisited

We prove a negative result concerning error reduction by parallel repetition for computationally sound protocols, e.g., interactive arguments. Our main result is a complete and computationally sound eight round interactive argument for which k-fold parallel repetition does not reduce the error below a constant for any polynomial k.     

Social and Heuristic Approaches to Credibility Evaluation Online

The tremendous amount of information available online has resulted in considerable research on information and source credibility. The vast majority of scholars, however, assume that individuals work in isolation to form credibility opinions and that people must assess information credibility in an effortful and time‐consuming manner. Focus group data from 109 participants were used to examine these assumptions. Results show that most users rely on others to make credibility assessments, often through the use of group‐based tools. Results also indicate that rather than systematically processing information, participants routinely invoked cognitive heuristics to evaluate the credibility of information and sources online. These findings are leveraged to suggest a number of avenues for further credibility theorizing, research, and practice.     

Selective Use of News Cues: A Multiple‐Motive Perspective on Information Selection in Social Media Environments

This study investigated the effects of message and social cues on selective exposure to political information in a social media environment. Based on the heuristic‐systematic model, we hypothesized that readers' selective consideration of specific cues can be explained by situational motivations. In an experiment (N = 137), subjects primed with motivational goals (accuracy, defense, or impression motivations, as well as a control group) were asked to search for information. Participants preferred attitude‐consistent information and balanced information over attitude‐inconsistent information, and also preferred highly recommended articles. Defense‐motivated partisans exhibited a stronger confirmation bias, whereas impression motivation amplified the effects of social recommendations. These findings specify the conditions under which individuals engage in narrow, open‐minded, or social patterns of information selection.     

Effects of Unresolved Factual Disputes in the News on Epistemic Political Efficacy

This experiment tests effects of passive, neutral reporting of contradictory factual claims on audiences. Exposure to such reporting is found to affect a new self‐efficacy construct developed in this study called epistemic political efficacy (EPE), which taps confidence in one's own ability to determine truth in politics. Measurement of EPE is found to be reliable and valid, and effects of neutral reporting on it are found to be conditional on prior interest in the issues under dispute. Implications of this effect and of EPE are discussed. Self‐efficacy theory ( Bandura, 1982 ) suggests these short‐term effects may accumulate over time. EPE may affect outcomes related to political understanding, opinion formation, and information seeking.     

Activity recognition in video sequences over qualitative abstracts of a diagram-based representation schema

Explicit reasoning over a spatial substrate, i.e., space–time information structures underlying a spatial problem, simplifies reasoning. Diagrammatic reasoning makes use of diagrams for exploiting such underlying structures. This paper proposes a novel approach combining diagrammatic reasoning with qualitative spatial and temporal reasoning techniques to visualize and perceive spatio-temporal relations among objects in a video. The hybrid techniques explore information over the spatial substrate for relational extractions. Different relations among objects in transition define short-term activities. Mealy machines are learned over patterns of short-term activities as activity recognizers. The proposed representation and recognition mechanism is validated by conducting experiments for video activity recognition from DARPA Mind’s Eye and J-HMDB dataset.     

The Effects of Negativity and Motivated Information Processing During a Political Campaign

This research investigated how voters select, process, are affected by, and recall political information in a dynamic campaign environment. It was hypothesized that voters' information selection, processing, and recall are subject to a negativity bias (i.e., negative information dominates over positive information), a congruency bias (i.e., positive information about the preferred candidate and negative information about the opponent candidate dominate over negative information about the preferred candidate and positive information about the opponent), and a candidate bias (i.e., information about the preferred candidate dominates over information about the opponent). Motivated by an initial candidate preference, participants were also expected to develop more polarized candidate evaluations over time. Participants were exposed to quickly changing information in the form of newspaper-style headlines on a dynamic, computer-based information board. The results generally supported negativity bias and candidate bias, whereas congruency bias was only found during information recall. At the information selection and processing stages, participants with a strong initial candidate preference showed a disproportionate preference for negative information about the preferred candidate. However, they developed more positive attitudes at the evaluation and recall stage. This finding suggests that participants were engaged in motivated information processing by counterarguing negative information about their preferred candidate.     

FAPbI3 Flexible Solar Cells with a Record Efficiency of 19.38% Fabricated in Air via Ligand and Additive Synergetic Process

Compared with silicon‐based solar cells, organic–inorganic hybrid perovskite solar cells (PSCs) possess a distinct advantage, i.e., its application in the flexible field. However, the efficiency of the flexible device is still lower than that of the rigid one. First, it is found that the dense formamidinium (FA)‐based perovskite film can be obtained with the help of N‐methyl‐2‐pyrrolidone (NMP) via low pressure‐assisted method. In addition, CH₃NH₃Cl (MACl) as the additive can preferentially form MAPbCl_3?xI_x perovskite seeds to induce perovskite phase transition and crystal growth. Finally, by using FAI·PbI₂·NMP+x%MACl as the precursor, i.e., ligand and additive synergetic process, a FA‐based perovskite film with a large grain size, high crystallinity, and low trap density is obtained on a flexible substrate under ambient conditions due to the synergetic effect, e.g., MACl can enhance the crystallization of the intermediate phase of FAI·PbI₂·NMP. As a result, a record efficiency of 19.38% in flexible planar PSCs is achieved, and it can retain about 89% of its initial power conversion efficiency (PCE) after 230 days without encapsulation under ambient conditions. The PCE retains 92% of the initial value after 500 bending cycles with a bending radii of 10 mm. The results show a robust way to fabricate highly efficient flexible PSCs.     

Highly Conductive,Scalable, and Machine Washable Graphene‐Based E‐Textiles for Multifunctional Wearable Electronic Applications

Graphene‐based textiles show promise for next‐generation wearable electronic applications due to their advantages over metal‐based technologies. However, current reduced graphene oxide (rGO)‐based electronic textiles (e‐textiles) suffer from poor electrical conductivity and higher power consumption. Here, highly conductive, ultraflexible, and machine washable graphene‐based wearable e‐textiles are reported. A simple and scalable pad?dry?cure method with subsequent roller compression and a fine encapsulation of graphene flakes is used. The graphene‐based wearable e‐textiles thus produced provide lowest sheet resistance (≈11.9 Ω sq^?1) ever reported on graphene e‐textiles, and highly conductive even after 10 home laundry washing cycles. Moreover, it exhibits extremely high flexibility, bendability, and compressibility as it shows repeatable response in both forward and backward directions before and after home laundry washing cycles. The scalability and multifunctional applications of such highly conductive graphene‐based wearable e‐textiles are demonstrated as ultraflexible supercapacitor and skin‐mounted strain sensors.     

E‐MAC: an elastic MAC layer for IEEE 802.11 networks

We present a system for real‐time traffic support in infrastructure and ad hoc IEEE 802.11 networks. The proposed elastic MAC (E‐MAC) protocol provides a distributed transmission schedule for stations with real‐time traffic requirements, while allowing a seamless coexistence with standard IEEE 802.11 clients, protecting best‐effort 802.11 traffic from starvation by means of admission control policies. Our scheduling decisions are based on an ‘elastic’ transmission opportunity (TXOP) assignment which allows for efficient wireless resource usage: whenever a real‐time station does not use the assigned TXOP, the other real‐time stations can take over the unused access opportunity, thus preventing the well‐known inefficiencies of static time division multiple access (TDMA) schemes. Unlike other TDMA‐based solutions for 802.11, E‐MAC does not require a tight synchronization among the participating clients, thus allowing its implementation on commodity WLAN hardware via minor software changes at the client side, and no changes at the access points (APs). We studied the performance of our mechanism via ns‐2 simulations and a mathematical model, showing that it outperforms IEEE 802.11e in terms of throughput, delay, and jitter. We finally provide a proof of concept through the results obtained in a real testbed where we implemented the E‐MAC protocol. Copyright © 2011 John Wiley & Sons, Ltd.     

Enzymatic Writing to Soft Films: Potential to Filter,Store, and Analyze Biologically Relevant Chemical Information

Sensor‐based chemical analyses commonly enlist either the molecular recognition capabilities of biology (e.g., enzyme biosensors) or advanced information processing algorithms (e.g., the electronic nose). Here, a hybrid approach is proposed in which an enzyme is used to “filter” chemical information and write this information to a film which then serves as a permanent storage medium that can be ‘read’ repeatedly, interactively, and by multiple sensor modalities. This approach is demonstrated by analyzing common dietary phenols that are reported to offer health benefits. Specifically, the enzyme tyrosinase is used to convert these phenols into reactive quinones that graft (i.e., write) to a chitosan film. Grafting can be detected by optical, mechanical, and electrochemical sensors. Importantly, grafting confers redox activity to the films and this redox activity can be probed interactively by advanced electrochemical methods that allow the intrinsic redox reactivities to be compared, redox interactions to be identified, and biologically relevant redox activities to be examined. The transfer of chemical and biological information to a film is envisioned to provide broader access to the extensive capabilities offered by sensor technologies and signal processing methodologies.     

A novel IEEE 802.11‐based MAC protocol supporting cooperative communications

Cooperative diversity is a transmission technique, where multiple terminals form a virtual antenna array that realizes spatial diversity gain in a distributed fashion. The concept of cooperation has already been introduced to MAC layer to design MAC protocol. But it does not take advantage of physical layer's cooperation. In this paper, we present a novel MAC protocol based on IEEE 802.11, called C‐MAC, which is able to support the basic building block of cooperative system. In other words, in C‐MAC, a source would invite a relay node into data transmission if there exits an available one. During data transmission, the source sends the signal to destination in the first time slot. The relay node will retransmit the overheard information to the destination in the second time slot. The destination combines two signals from the source and the helper to create the spatial diversity and robustness against channel fading. The C‐MAC is backward compatible to the legacy IEEE 802.11 system. The performance of C‐MAC mainly depends on physical layer's performance as it just provides the support for cooperation at the MAC layer. If the physical layer works well, C‐MAC would outperform IEEE 802.11 when considering packet error rate (PER). We also perform extensive simulation using ns‐2 with assumptive physical parameters. The results show that C‐MAC would outperform 802.11 if PER is over some threshold, e.g. when PER is 0.4, C‐MAC can achieve up to 11.5% higher throughput than IEEE 802.11. Copyright © 2011 John Wiley & Sons, Ltd.     

Multi‐carrier platform for wireless communications. Part 2: OFDM and MC‐CDMA systems with high‐performance,high‐throughput via innovations in spreading

Multi‐carrier technologies in general, and OFDM and MC‐CDMA in particular, are an integral part of the wireless landscape. In this second part of a two‐part survey, the authors present an innovative set of spreading codes known as CI codes, and demonstrate how these significantly increase performance and capacity in OFDM and MC‐CDMA systems, all the while eliminating PAPR concerns. Regarding OFDM: the spreading of each symbol over all N carriers using CI spreading codes (replacing the current one symbol per carrier strategy) are presented. CI codes are ideally suited for spreading OFDM since, when compared to traditional OFDM, CI‐based OFDM systems achieve the performance of coded OFDM (COFDM) while maintaining the throughput of uncoded OFDM, and, at the same time, eliminate PAPR concerns. When applied to MC‐CDMA, CI codes provide a simple means of supporting 2N users on N carriers while maintaining the performance of an N‐user Hadamard Walsh code MC‐CDMA system, i.e., CI codes double MC‐CDMA network capacity without loss in performance. The CI codes used in OFDM and MC‐CDMA systems are directly related to the CI pulse (chip) shapes used to enhance TDMA and DS‐CDMA (see part 1): hence, the CI approach provides a common hardware platform for today's multi‐carrier/multiple‐access technologies, enabling software radio applications. Copyright © 2002 John Wiley & Sons, Ltd.     

SYNC‐NET: distributed time synchronization in clustered sensor networks

Time synchronization is essential for several ad‐hoc network protocols and applications, such as TDMA scheduling and data aggregation. In this paper, we propose a time synchronization framework for clustered, multi‐hop sensor networks. We assume that relative node synchronization is sufficient, that is, consensus on one time value is not required. Our goal is to divide the network into connected synchronization regions (nodes within two‐hops) and perform inter‐regional synchronization in O(LLSync) × N_iter time, where O(LLSync) denotes the complexity of the underlying low‐level synchronization technique (used for single‐hop synchronization), and N_iter denotes the number of iterations where the low‐level synchronization protocol is invoked. Thus, our main objective is rapid convergence. We propose novel fully distributed protocols, SYNC‐IN and SYNC‐NET, for regional and network synchronization, respectively, and prove that N_iter is O(1) for all protocols. Our framework does not require any special node capabilities (e.g., being global positioning systems (GPS)‐enabled), or the presence of reference nodes in the network. Our framework is also independent of the particular clustering, inter‐cluster routing, and low‐level synchronization protocols. We formulate a density model for analyzing inter‐regional synchronization, and evaluate our protocols via extensive simulations. Copyright © 2007 John Wiley & Sons, Ltd.     

Systems design means process precision,but emphasizes culture,value, and results

The issue: What does a comprehensive internal dispute resolution system look like? The problems: Is it current? Is it responsive? Is it effective? The perspective: Melanie Lewis, of Atlanta, describes how Coca‐Cola Enterprises Inc. assesses its conflict resolution needs, as well as how it implements, operates, and monitors its program–including provisions to redesign for new developments     

“OK,Google, why do I use you?” Motivations,post-consumption evaluations,and perceptions of voice AI assistants

Voice-activated, artificial intelligence–based assistants (voice AI assistants) have become an integral part of everyday life because they can be easily activated to complete numerous tasks. However, little is known about what motivates people to use them or how these motivations influence users’ post-consumption evaluations and perceptions. This study develops measures to capture uses and gratifications related to voice AI assistants. It identifies five primary motivations for use—social interaction, personal identity, conformity, life efficiency, and information. Results show that the utilitarian motivations of life efficiency and information influence all post-consumption evaluations and behavioral intentions positively (i.e., users’ attitudes, satisfaction, and intentions to continue using voice AI assistants). However, social motivations are also important. Social interaction and conformity motivations also influence user satisfaction, and the conformity motivation shapes individuals’ intentions to continue using voice AI assistants. The findings further demonstrate that users’ motivations influence perceptions of their voice AI assistants’ roles. In keeping with the “Computers Are Social Actors” (CASA) paradigm, users motivated by social interaction are likely to perceive a voice AI assistant as socially attractive and as a friend, whereas users motivated by life efficiency are likely to perceive it as an assistant. Users motivated by information are more likely to perceive a voice AI assistant as technology, while those motivated by social interaction are less likely to do so. The implications of these findings are discussed, and recommendations for future research are provided.     

The Era of Digital Health: A Review of Portable and Wearable Affinity Biosensors

Digital health facilitated by wearable/portable electronics and big data analytics holds great potential in empowering patients with real‐time diagnostics tools and information. The detection of a majority of biomarkers at trace levels in body fluids using mobile health (mHealth) devices requires bioaffinity sensors that rely on “bioreceptors” for specific recognition. Portable point‐of‐care testing (POCT) bioaffinity sensors have demonstrated their broad utility for diverse applications ranging from health monitoring to disease diagnosis and management. In addition, flexible and stretchable electronics‐enabled wearable platforms have emerged in the past decade as an interesting approach in the ambulatory collection of real‐time data. Herein, the technological advancements of mHealth bioaffinity sensors evolved from laboratory assays to portable POCT devices, and to wearable electronics, are synthesized. The involved recognition events in the mHealth affinity biosensors enabled by bioreceptors (e.g., antibodies, DNAs, aptamers, and molecularly imprinted polymers) are discussed along with their transduction mechanisms (e.g., electrochemical and optical) and system‐level integration technologies. Finally, an outlook of the field is provided and key technological bottlenecks to overcome identified, in order to achieve a new sensing paradigm in wearable bioaffinity platforms.     

Soft ARQ for Layered Streaming Media

A growing and important class of traffic in the Internet is so-called “streaming media,” in which a server transmits a packetized multimedia signal to a receiver that buffers the packets for playback. This playback buffer, if adequately sized, counteracts the adverse impact of delay jitter and reordering suffered by packets as they traverse the network, and if large enough also allows lost packets to be retransmitted before their playback deadline expires. We call this framework for retransmitting lost streaming-media packets “soft ARQ” since it represents a relaxed form of Automatic Repeat reQuest (ARQ). While state-of-the-art media servers employ such strategies, no work to date has proposed an optimal strategy for delay-constrained retransmissions of streaming media—specifically, one which determines what is the optimal packet to transmit at any given point in time. In this paper, we address this issue and present a framework for streaming media retransmission based on layered media representations, in which a signal is decomposed into a discrete number of layers and each successive layer provides enhanced quality. In our approach, the source chooses between transmitting (1) newer but critical coarse information (e.g., a first approximation of the media signal) and (2) older but less important refinement information (e.g., added details) using a decision process that minimizes the expected signal distortion at the receiver. To arrive at the proper mix of these two extreme strategies, we derive an optimal strategy for transmitting layered data over a binary erasure channel with instantaneous feedback. To provide a quantitative performance comparison of different transmission policies, we conduct a Markov-chain analysis, which shows that the best transmission policy is time-invariant and thus does not change as the frames' layers approach their expiration times.     

An overview of online charging in 3GPP networks: new ways of utilizing user,network, and service‐related information

Modern charging systems routinely apply the user, network, and service‐related information while performing online charging. Compared, however, to all the information available to and used in managing the network as a whole, the charging systems only use a limited subset. This work is motivated by the challenge to identify which information is used, and how it is used in online charging‐related processes, and also to explore whether it could be utilized ‘better’ or ‘smarter’ to improve future online charging systems functionality. We do not attempt to predict which information will be utilized in such systems and for what purpose, but instead summarize the open issues in view of the emerging trend of exploiting the user, network and service‐related information in service provisioning. We focus on the most recent 3GPP standards and relevant research papers, and propose three key aspects of online charging, with respect to information utilization: (a) signaling aspect, (b) inter‐domain aspect, and (c) service‐ and component‐based aspect. We present a state‐of‐the‐art review by grouping the works found in the literature based on the aspects they are associated with, and compare them based on the proposed comparison criteria. The discussion presented at the end of the paper indicates three common open issues, namely: (1) lack of common charging information specification and structure; (2) lack of mechanisms for information sharing among stakeholders in the service delivery process; and (3) lack of a common framework for sharing information while protecting user privacy. Copyright © 2012 John Wiley & Sons, Ltd.