Coding Strategies for Noise-Free Relay Cascades with Half-Duplex Constraint

Two types of noise-free relay cascades are investigated. Networks where a source communicates with a distant receiver via a cascade of half-duplex constrained relays, and networks where not only the source but also a single relay node intends to transmit information to the same destination. We introduce two relay channel models, capturing the half-duplex constraint, and within the framework of these models capacity is determined for the first network type. It turns out that capacity is significantly higher than the rates which are achievable with a straightforward time-sharing approach. A capacity achieving coding strategy is presented based on allocating the transmit and receive time slots of a node in dependence of the node's previously received data. For the networks of the second type, an upper bound to the rate region is derived from the cut-set bound. Further, achievability of the cut-set bound in the single relay case is shown given that the source rate exceeds a certain minimum value.Comment: Proceedings of the 2008 IEEE International Symposium on Information Theory, Toronto, ON, Canada, July 6 - 11, 200

Capacity for Half-Duplex Line Networks with Two Sources

The focus is on noise-free half-duplex line networks with two sources where the first node and either the second node or the second-last node in the cascade act as sources. In both cases, we establish the capacity region of rates at which both sources can transmit independent information to a common sink. The achievability scheme presented for the first case is constructive while the achievability scheme for the second case is based on a random coding argument.Comment: Proceedings of the IEEE International Symposium on Information Theory, Austin, TX, USA, June 12 - 18, 201

Root causes and improvement proposals for cost overrun in projects: A contractor's perspective

Project costs tend to overrun, regardless of the size and type of the project. Research has shown that little progress has been made in this field. The problem also applies to contractors, which repeatedly struggle to stay on budget and therefore face cost overruns in their projects. This study aims to locate the root causes of cost overrun in the projects of the case company, which is a global technology company. Moreover, areas for improvement are proposed for the mitigation of future cost overruns. To do so, several theories and methodologies are applied: The RAL concept, the Analytical Hierarchy Process, the Critical Factor Indexes, the Sense and Respond methodology, the Manufacturing Strategy Index, the Sustainable Competitive Ad-vantage method, and Knowledge and Technology. Two questionnaires were used for the data collection and were answered by a total of 18 respondents. Besides, interviews were carried out to get background information and to validate the results with the Weak Market Test. This study focuses on the engineering process and the site management process of the projects, which contribute the most to the cost overruns of the case company. Challenges in resource management and the cooperation with the client were found to be the root causes of cost overrun in the examined projects. To mitigate future cost overruns, it was proposed to lay a special focus on Project Scheduling, Basic Design, Detailed Design, and Off-site Validation. Moreover, improvements in Resource Management, uniform working directives, and special attention to new clients and clients with consultants contribute to the mitigation of future cost overruns. The Knowledge and Technology results indicate that the products and services of the case company are in the maturity phase of the technology life cycle. Thus, a reduction in production costs is suggested. The highest uncertainty is related to core technology, hence investments in core technology will further contribute to the success of future projects

A possible deuterium anomaly: Implications of the CH3D/CH4 mixing ratios in the atmospheres of Jupiter, Saturn, and Uranus

Observations of CH3D in the atmospheres of the outer planets provide a test of the theory of deuterium fractionation equilibrium in the formation and evolution of these planets. Recent measurements of the CH3D/CH4 mixing ratios made for Saturn and Uranus are presented and intercompared with current values of Jupiter, illustrating large differences between the planets. Their implied D/H ratios are compared to D/H ratios derived from measurements of HD/H2; and, in the cases of Jupiter and Saturn, they may be incompatible. Implications of these comparisons are discussed in terms of the deuterium fractionation chemistry and possible enrichments of deuterium in the core ices of the planets