The Wiretap Channel with Feedback: Encryption over the Channel

In this work, the critical role of noisy feedback in enhancing the secrecy capacity of the wiretap channel is established. Unlike previous works, where a noiseless public discussion channel is used for feedback, the feed-forward and feedback signals share the same noisy channel in the present model. Quite interestingly, this noisy feedback model is shown to be more advantageous in the current setting. More specifically, the discrete memoryless modulo-additive channel with a full-duplex destination node is considered first, and it is shown that the judicious use of feedback increases the perfect secrecy capacity to the capacity of the source-destination channel in the absence of the wiretapper. In the achievability scheme, the feedback signal corresponds to a private key, known only to the destination. In the half-duplex scheme, a novel feedback technique that always achieves a positive perfect secrecy rate (even when the source-wiretapper channel is less noisy than the source-destination channel) is proposed. These results hinge on the modulo-additive property of the channel, which is exploited by the destination to perform encryption over the channel without revealing its key to the source. Finally, this scheme is extended to the continuous real valued modulo-$\Lambda$ channel where it is shown that the perfect secrecy capacity with feedback is also equal to the capacity in the absence of the wiretapper.Comment: Submitted to IEEE Transactions on Information Theor

Application of Diffusion – And Perfusion – Weighted Imaging in Acute Ischemic Stroke

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Cognitive Medium Access: Exploration, Exploitation and Competition

This paper establishes the equivalence between cognitive medium access and the competitive multi-armed bandit problem. First, the scenario in which a single cognitive user wishes to opportunistically exploit the availability of empty frequency bands in the spectrum with multiple bands is considered. In this scenario, the availability probability of each channel is unknown to the cognitive user a priori. Hence efficient medium access strategies must strike a balance between exploring the availability of other free channels and exploiting the opportunities identified thus far. By adopting a Bayesian approach for this classical bandit problem, the optimal medium access strategy is derived and its underlying recursive structure is illustrated via examples. To avoid the prohibitive computational complexity of the optimal strategy, a low complexity asymptotically optimal strategy is developed. The proposed strategy does not require any prior statistical knowledge about the traffic pattern on the different channels. Next, the multi-cognitive user scenario is considered and low complexity medium access protocols, which strike the optimal balance between exploration and exploitation in such competitive environments, are developed. Finally, this formalism is extended to the case in which each cognitive user is capable of sensing and using multiple channels simultaneously.Comment: Submitted to IEEE/ACM Trans. on Networking, 14 pages, 2 figure

Intranet-based Training Facilities ERP System Implementation: A Case Study

Enterprise Resource Planning (ERP) systems enable organizations to gain better control over their operations and costs by tightly integrating related business functions. This results in substantial savings. They provide a migration path from legacy systems to a client server environment. They also offer a solution to the year 2000 problem. This has led to a sharp increase in the demand for these systems. Implementation of ERP systems, however, is considered to be a high cost high risk project. Training is a key factor in implementation success. ERP implementation affects the roles of a large number of employees in an organization, who must be trained within a relatively short time period. Organizing and delivering such training in a cost effective and timely manner is a challenging task. Trainers are using innovative methods to accomplish this. Web- based training is recently gaining popularity as a convenient and economical means for imparting training to a large group of widely dispersed audience. In this article we describe an innovative use of intranet-based training to facilitate ERP implementation in a manufacturing organization

The Effect of Switching Costs on the Satisfaction-Continuance Relationship: An Extension of Expectation-Confirmation Model

The expectation-confirmation model (ECM) has been applied to investigate the satisfaction with and continuance of information technology (IT) after its adoption. However, the ECM assumes that the satisfaction-continuance relationship is linear. In the electronics market, however, such a linear relationship may be susceptible to the influence of new variants unique to the Internet. In addition, the ECM-based satisfaction-continuance relationship explains psychological motives for IS continuance nicely, but its framework is insufficient to capture the non-psychological dimensions of IS continuance intention. Subsequently, the inclusion of switching costs, which has been frequently proposed as a determinant of loyalty and a moderator of the satisfaction-loyalty relationship, as a construct of ECM may enrich our understanding of the continuance and the satisfaction-continuance relationship of online services. The addition of switching costs can also improve the theoretical completeness of the model, particularly in the online services context

An Empirical Investigation of Bidding Strategies and Their Effects on Online Single-Unit Auctions

Online bidding strategy is one of the most discussed topics in online auction research. This research aims to empirically confirm online bidding strategies in single-unit auctions and evaluate these strategies in the context of auction winning outcome, final price evaluation, and perceived enjoyment. Both objective and subjective data of online single-unit auctions were collected to validate our postulated hypotheses. Our findings suggest that there are three basic bidding strategies in single-unit auctions and they indeed have different impacts on auction biddings