Individual Messages Research Articles

Joint Channel Estimation and Channel Decoding in Physical-Layer Network Coding Systems: An EM-BP Factor Graph Framework

This paper addresses the problem of joint channel estimation and channel decoding in physical-layer network coding (PNC) systems. In PNC, multiple users transmit to a relay simultaneously. PNC channel decoding is different from conventional multi-user channel decoding: specifically, the PNC relay aims to decode a network-coded message rather than the individual messages of the users. Although prior work has shown that PNC can significantly improve the throughput of a relay network, the improvement is predicated on the availability of accurate channel estimates. Channel estimation in PNC, however, can be particularly challenging because of 1) the overlapped signals of multiple users; 2) the correlations among data symbols induced by channel coding; and 3) time-varying channels. We combine the expectation-maximization (EM) algorithm and belief propagation (BP) algorithm on a unified factor-graph framework to tackle these challenges. In this framework, channel estimation is performed by an EM subgraph, and channel decoding is performed by a BP subgraph that models a virtual encoder matched to the target of PNC channel decoding. Iterative message passing between these two subgraphs allow the optimal solutions for both to be approached progressively. We present extensive simulation results demonstrating the superiority of our PNC receivers over other PNC receivers.

Impact of malaria related messages on insecticide-treated net (ITN) use for malaria prevention in Ghana

BackgroundMedia messages have been used in Ghana to promote insecticide-treated net (ITN)/bed net usage in an effort to impact on malaria prevention. The aim of this study was to assess the effect of such malaria-related messages delivered through electronic/print media and by volunteers/health workers on the use of ITNs by children living in a household.MethodsData was collected from September to November of 2008 using a structured, interviewer-administered questionnaire by the Ghana Statistical Service as part of a national demographic and health survey (DHS). Secondary data analysis was performed on the collected data using multivariate logistic regression for both individual messages and a composite (any of) message variable.ResultsFrom the 11,788 households surveyed, 45% had at least one net. Households with male heads were more likely to have a child sleeping under a bed net the previous night (p = 0.0001). Individual Messages delivered by a health worker or a dedicated radio programme, had the highest effect for one or more children sleeping under a net the night before (OR adjusted = 1.65; 95% CI = 1.44 to 1.88 and OR adjusted = 1.26; 95% CI =1.12 to 1.42 respectively) while hearing any of the eight messages (composite score) resulted in the highest odds for one or more children (OR adjusted = 3.06; 95% CI = 2.27 to 4.12) sleeping under a bed net.ConclusionEfforts to relate ITN messages to the public are very useful in increasing use of bed nets and having multiple ways of reaching the public increases their effect, with the biggest effect seen when health workers and volunteers were used to deliver malaria-related messages to the public.

Predicting crime using Twitter and kernel density estimation

Twitter is used extensively in the United States as well as globally, creating many opportunities to augment decision support systems with Twitter-driven predictive analytics. Twitter is an ideal data source for decision support: its users, who number in the millions, publicly discuss events, emotions, and innumerable other topics; its content is authored and distributed in real time at no charge; and individual messages (also known as tweets) are often tagged with precise spatial and temporal coordinates. This article presents research investigating the use of spatiotemporally tagged tweets for crime prediction. We use Twitter-specific linguistic analysis and statistical topic modeling to automatically identify discussion topics across a major city in the United States. We then incorporate these topics into a crime prediction model and show that, for 19 of the 25 crime types we studied, the addition of Twitter data improves crime prediction performance versus a standard approach based on kernel density estimation. We identify a number of performance bottlenecks that could impact the use of Twitter in an actual decision support system. We also point out important areas of future work for this research, including deeper semantic analysis of message content, temporal modeling, and incorporation of auxiliary data sources. This research has implications specifically for criminal justice decision makers in charge of resource allocation for crime prevention. More generally, this research has implications for decision makers concerned with geographic spaces occupied by Twitter-using individuals.

Determinants of HIV testing among young people aged 18 - 24 years in South Africa.

Although recent estimates of the HIV/AIDS burden in South Africa show the particular vulnerability of youth to HIV, HIV testing and its determinants are largely understudied in this age group. To investigate the prevalence and determinants of HIV testing among young people aged 18 to 24 years, as part of an evaluation of the impact of loveLife. South Africa's national HIV prevention campaign for young people, on HIV and related risk behaviours. A cross-sectional population-based household survey was conducted using a multistage stratified cluster sampling approach. The total sample included 3123 participants, aged 18-24, 54.6% men and 45.4% women, from four provinces (Eastern Cape, Gauteng, KwaZulu-Natal and Mpumalanga). The results indicated that over half (52.2%) of the youth reported testing for HIV, with more young females (60.1%) testing for HIV compared to their male counterparts (39.9%). In the multivariate analysis, older age, being female, HIV knowledge, having ever talked to the mother or female guardian about HIV and having ever been pregnant or made someone pregnant were found to be associated with testing for HIV. There is still room for improving the low proportion of young people who test for HIV. Specific attention needs to be paid to younger males, with lack of HIV knowledge, having never talked to the mother or female guardian about HIV and having never been pregnant or made someone pregnant were less likely to be tested. Outreach at individual and community levels and public health messages targeting these youth should be implemented.

Nursing problem-based learning activity: Song writing and singing

The function of song is not only to deliver individual's messages, but also to serve as a learning approach to facilitate students' learning. To observe the effectiveness of songs in facilitating students' learning, a Problem-based Learning (PBL) class with twenty students was divided into four groups with five students per group. Each group was asked to write a song based on two given scenarios, to sing the song out loud, and to participate in a follow-up focus group interview afterwards. The four songs reflected the students' understanding of academic knowledge and their perspectives toward the protagonists in the presented scenarios. Two songs are presented in this paper to demonstrate how the approach was carried out in the nursing PBL class. This paper aims to show the implication of song writing and singing in PBL and shed some light on teaching and learning.

Becoming More Reflective about the Role of Design in Communication

Robert Craig's constitutive meta-model of communication reminds us that while communication scholarship may feel like discovery of communication's natural properties, it is also often (if not always) on a path to invention of new possibilities and reconstitution. The constitutive meta-model suggests that every theory of communication is also a design language for communication, and that design itself may be a path to theory development. Design inquiry can be conducted in all subdisciplines of communication, incorporating and contributing to widely disparate communication theories. Design work itself takes many forms, producing artifacts as diverse as individual messages, persuasive campaigns, interaction protocols, large-scale participation frameworks for public decision-making, and more. This special issue explores design scholarship in the field of communication, with five original essays representing different subfields and different theoretical approaches. In this introduction, we argue that design work is more than application of theory; design itself is a theory-building enterprise. It is a distinct form of inquiry that builds new knowledge, complementary to, but different in kind from, empirical and critical scholarship.

INFORMATION POSSIBILITY OF MESSAGES OF DISCRETE SYMBOLS

In the article is offered a combinatory approach for determination of information possibility of individual messages of discrete sources as quantity of information in them when taken into account recurrent alphabetic symbols and structural uniformity allowing to estimate and to optimize information possibilities of the used messages.

Innovation from Imitation: Error Correction in Networks Reduces Accuracy and Promotes Innovation

An enormous body of scholarship examines how social contagions spread over social networks. But despite the fact that humans make mistakes, diffusion through social networks is typically modeled as though information is relayed with perfect fidelity. As a result, little is known about how errors, the robustness of message formats, and attempts to correct errors, impact the spread of contagions. We find in an experiment using human subjects that compact (high entropy) message formats, such as text messaging pidgin, are more prone to error than more expansive (lower entropy) formats, such as standard English. We also find that while efforts to correct mistakes improve the accuracy of individual messages, over time they paradoxically generate a wider variety of mutant forms of the contagion than would result from a lack of correction. This indicates that the ability of messages to cross even “small- world” human social networks may be overestimated and that models of social contagion and diffusion are biased...

Towards identifying unresolved discussions in student online forums

Automatic tools for analyzing student online discussions are highly desirable for providing better assistance and promoting discussion participation. This paper presents an approach for identifying student discussions with unresolved issues or unanswered questions. In order to handle highly incoherent data, we perform several data processing steps. We then apply a two-phase classification algorithm. First, we classify of individual messages to identify the roles that the messages play, such as question, issue raising, and answers. We then use the resulting speech acts as features for classifying discussion threads with unanswered questions or unresolved issues. We performed a preliminary analysis of the classifiers and the system shows an average F score of 0.76 in discussion thread classification.

Through a PRISM Darkly: Surveillance and Speech Suppression in the 'Post-Democracy Electronic State'

Through a PRISM Darkly: Surveillance and Speech Suppression in the 'Post-Democracy Electronic State'

LARGE PAYLOAD BIDIRECTIONAL QUANTUM SECURE DIRECT COMMUNICATION WITHOUT INFORMATION LEAKAGE

A large payload bidirectional quantum secure direct communication (BQSDC) protocol without information leakage is proposed, which is based on entanglement swapping between any two Greenberger–Horne–Zeilinger (GHZ) states. Two remote authorized parties, Alice and Bob, can safely exchange their individual secret messages without worrying about the information leakage problem. Our protocol uses a shared secret GHZ state to overcome the information leakage problem. The shared secret GHZ state plays two roles in the bidirectional communication process: on one hand, it lets Bob know the prepared initial state; on the other hand, it is used for encoding Bob's secret messages. Moreover, our protocol can transmit six bits of secret messages per round communication. Compared with those previous BQSDC protocols, the advantage of our protocol lies in having the following two characters simultaneously: on one hand, it overcomes the information leakage problem; one the other hand, its capacity is as high as six bits per round communication.

“I, Me, Mine” or “Us, We, Ours?”: The Influence of Cultural Psychology on Web-Based Customization

A profusion of recent research on consumer responses to individualized messages points to an enduring interest in the psychology of web-based customization. Across disciplines, the consensus is that highly individualized messages will generate more favorable outcomes than less individualized ones because they match message recipients' need for unique self-identity. We challenge this popular notion by arguing that highly individualized messages will not be as effective in collectivistic cultures that discourage unique self-identity. We test this proposition in a 2 × 3 experiment by randomly assigning participants (N = 120) representing either an individualistic or collectivistic culture (American, Chinese, respectively) to one of two levels of a customized message (highly individualized vs. less highly individualized) or a noncustomized, generic message (control condition). The experimental findings suggest a significant mediated moderation effect: Culture moderates the relationship between message type and attitude such that American participants report a more favorable attitude toward highly individualized messages and Chinese participants report a more favorable attitude toward less highly individualized messages, and this moderation is mediated by a psychological sense of community. Besides theoretical implications, we also highlight an original methodological procedure for manipulating customized messages in online environments.

Capacity Region of Cooperative Multiple-Access Channel With States

We consider a two-user state-dependent multiaccess channel in which the states of the channel are known noncausally to one of the encoders and only strictly causally to the other encoder. Both encoders transmit a common message and, in addition, the encoder that knows the states noncausally transmits an individual message. We find explicit characterizations of the capacity region of this communication model in both discrete memoryless and memoryless Gaussian cases. In particular, the capacity region analysis demonstrates the utility of the knowledge of the states only strictly causally at the encoder that sends only the common message in general. More specifically, in the discrete memoryless setting, we show that such a knowledge is beneficial and increases the capacity region in general. In the Gaussian setting, we show that such a knowledge does not help, and the capacity is same as if the states were completely unknown at the encoder that sends only the common message. Furthermore, we also study the special case in which the two encoders transmit only the common message and show that the knowledge of the states only strictly causally at the encoder that sends only the common message is not beneficial in this case, in both discrete memoryless and memoryless Gaussian settings. The analysis also reveals optimal ways of exploiting the knowledge of the state only strictly causally at the encoder that sends only the common message when such a knowledge is beneficial. The encoders collaborate to convey to the decoder a lossy version of the state, in addition to transmitting the information messages through a generalized Gel'fand–Pinsker binning. Particularly important in this problem are the questions of 1) optimal ways of performing the state compression and 2) whether or not the compression indices should be decoded uniquely. By developing two optimal coding schemes that perform this state compression differently, we show that when used as parts of appropriately tuned encoding and decoding processes, both compression à-la noisy network coding by Lim <etal xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"/> or the quantize-map-and-forward by Avestimeher <etal xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"/> , i.e., with no binning, and compression using Wyner–Ziv binning are optimal. The scheme that uses Wyner–Ziv binning shares elements with Cover and El Gamal original compress-and-forward, but differs from it mainly in that backward decoding is employed instead of forward decoding and the compression indices are not decoded uniquely. Finally, by exploring the properties of our outer bound, we show that, although not required in general, the compression indices can in fact be decoded uniquely essentially without altering the capacity region, but at the expense of larger alphabets sizes for the auxiliary random variables.

A Cross-Layer Approach to Privacy-Preserving Authentication in WAVE-Enabled VANETs

We present an anonymous authentication and verification scheme for the IEEE Wireless Access in Vehicular Communications (WAVE)-based vehicular ad hoc networks (VANETs). Our contribution includes vehicular message authentication and an efficient prioritized verification strategy for periodic road safety messages. A variation of elliptic curve digital signature algorithm (ECDSA) is used in combination with the identity-based (ID-based) signature, where current position information on a vehicle is utilized as the ID of the corresponding vehicle. This waives the need for a third-party public key certificate for message authentication in VANETs. A high-density road traffic condition poses a challenge for authentication of vehicular messages since the required verification time is often much longer than the average interarrival time. To mitigate the issue, messages of each traffic class are verified following the VANET's medium access control (MAC) layer priorities and the application relevance of individual safety messages. Performance analysis and simulation results have shown that our approach is secure, privacy preserving, scalable, and resource efficient.

Local communities' knowledge of lignite surface mining – sources and level of satisfaction: examples from central Poland

Abstract Developing of large-scale lignite excavation can often generate socio-environmental conflicts between mining-energy companies and various stakeholders, such as local communities or ecological organizations. In this context indication of potential channels of communication with local communities’ is needed to increase the level of their satisfaction with own knowledge and to optimize the social dialogue. The paper presents the results of a questionnaire survey conducted in selected communities of the Łódź voivodeship where surface mining exists at present (Kleszczów) or will be developed soon (Złoczew). They were realized with the Computer Assisted Telephone Interviewing on the representative groups of adults. The paper contains analysis of two selected closed-type questions: the first one concerned self-assessment of knowledge level of lignite mining, the second one - sources of information on mining activity. Previous media reports on mining activity in the examined areas were analysed, too. As it seems, various means of social communication should be used: television and radio are the major source of information for local communities, printing press and the Internet are important as well. A detailed set of communication channels and the content of individual messages should be carefully selected for specific target groups (depending on gender, age and education). It should be emphasized that a properly conducted public debate may prove to be one of the factors determining the success of mining-energy investments and sustainable development of some regions.

SIP Flow Time Interval between Messages of Statistical Analysis

SIP protocol is most often used for voice information transmitting over IP networks via communication session. Communication session process has been managed by SIP proxy server. In order to determine its operating characteristics, such as message service time, and message blocking probability, it is necessary to know the statistical features of the served traffic including the time interval of incoming message flow, the time interval distribution between arriving messages, mean value and their possible deviation. The statistic characteristics of time intervals of individual SIP messages and the total flow entering into SIP Proxy server have been experimentally determined in the paper. It has been found that the inter-arrival time of the sum total of SIP message flow does not correspond to the Poisson distribution thus General distribution should be used in the tests.DOI: http://dx.doi.org/10.5755/j01.eee.19.5.2908

Power lurking within individual messages

PurposeThis paper aims to review the latest management developments across the globe and pinpoint practical implications from cutting‐edge research and case studies.Design/methodology/approachThis briefing is prepared by an independent writer who adds their own impartial comments and places the articles in context.FindingsThere is something highly reassuring about the idea of a recommendation via word of mouth. People have chosen to speak highly of a service or product without any financial inducement.Practical implicationsThe paper provides strategic insights and practical thinking that have influenced some of the world's leading organizations.Originality/valueThe briefing saves busy executives and researchers hours of reading time by selecting only the very best, most pertinent information and presenting it in a condensed and easy‐to‐digest format.

On the Role of Mobility for Multimessage Gossip

We consider information dissemination in a large $n$-user wireless network in which $k$ users wish to share a unique message with all other users. Each of the $n$ users only has knowledge of its own contents and state information; this corresponds to a one-sided push-only scenario. The goal is to disseminate all messages efficiently, hopefully achieving an order-optimal spreading rate over unicast wireless random networks. First, we show that a random-push strategy -- where a user sends its own or a received packet at random -- is order-wise suboptimal in a random geometric graph: specifically, $\Omega(\sqrt{n})$ times slower than optimal spreading. It is known that this gap can be closed if each user has "full" mobility, since this effectively creates a complete graph. We instead consider velocity-constrained mobility where at each time slot the user moves locally using a discrete random walk with velocity $v(n)$ that is much lower than full mobility. We propose a simple two-stage dissemination strategy that alternates between individual message flooding ("self promotion") and random gossiping. We prove that this scheme achieves a close to optimal spreading rate (within only a logarithmic gap) as long as the velocity is at least $v(n)=\omega(\sqrt{\log n/k})$. The key insight is that the mixing property introduced by the partial mobility helps users to spread in space within a relatively short period compared to the optimal spreading time, which macroscopically mimics message dissemination over a complete graph.

Data mining agent conversations: A qualitative approach to multiagent systems analysis

This paper presents a novel method for analysing the behaviour of multiagent systems on the basis of the semantically rich information provided by agent communication languages and interaction protocols specified at the knowledge level. More low-level communication mechanisms only allow for a quantitative analysis of the occurrence of message types, the frequency of message sequences, and the empirical distributions of parameter values. Quite differently, the semantics of languages and protocols in multiagent systems can help to extract qualitative properties of observed conversations among agents. This can be achieved by interpreting the logical constraints associated with protocol execution paths or individual messages as the context of an observed interaction, and using them as features of learning samples. The contexts “mined” from such analyses, or context models, can then be used for various tasks, e.g. for predicting others’ future responses (useful when trying to make strategic communication decisions to achieve a particular outcome), to support ontological alignment (by comparing the properties of logical constraints attached to messages across participating agents), or to assess the trustworthiness of agents (by verifying the logical coherence of their behaviour). This paper details a formal approach that describes our notion of context models in multiagent conversations, an implementation of this approach in a practical tool for mining qualitative context models, and experimental results to illustrate its use and utility.

The Capacity Region of a Product of Two Unmatched Physically Degraded Gaussian Broadcast Channels With Three Individual Messages and a Common Message

This paper considers a Gaussian broadcast channel with two unmatched degraded components, three individual messages, and a common message that is intended for all three receivers. It is shown that for this channel, superposition coding with Gaussian signalling is sufficient to achieve every point in the capacity region.