Optimal threshold policies for admission control in communication networks via discrete parameter stochastic approximation

The problem of admission control of packets in communication networks is studied in the continuous time queueing framework under different classes of service and delayed information feedback. We develop and use a variant of a simulation based two timescale simultaneous perturbation stochastic approximation (SPSA) algorithm for finding an optimal feedback policy within the class of threshold type policies. Even though SPSA has originally been designed for continuous parameter optimization, its variant for the discrete parameter case is seen to work well. We give a proof of the hypothesis needed to show convergence of the algorithm on our setting along with a sketch of the convergence analysis. Extensive numerical experiments with the algorithm are illustrated for different parameter specifications. In particular, we study the effect of feedback delays on the system performance.

Key Factors Influencing Economic Relationships and Communication in Finnish Food Chains

The aim of this report is to discuss the role of the relationship type and communication in two Finnish food chains, namely the pig meat-to-sausage (pig meat chain) and the cereal-to-rye bread (rye chain) chains. Furthermore, the objective is to examine those factors influencing the choice of a relationship type and the sustainability of a business relationship. Altogether 1808 questionnaires were sent to producers, processors and retailers operating in these two chains of which 224 usable questionnaires were returned (the response rate being 12.4%). The great majority of the respondents (98.7%) were small businesses employing less than 50 people. Almost 70 per cent of the respondents were farmers. In both chains, formal contracts were stated to be the most important relationship type used with business partners. Although for many businesses written contracts are a common business practice, the essential role of the contracts was the security they provide regarding the demand/supply and quality issues. Relative to the choice of the relationship types, the main difference between the two chains emerged especially with the prevalence of spot markets and financial participation arrangements. The usage of spot markets was significantly more common in the rye chain when compared to the pig meat chain, while, on the other hand, financial participation arrangements were much more common among the businesses in the pig meat chain than in the rye chain. Furthermore, the analysis showed that most of the businesses in the pig meat chain claimed not to be free to choose the relationship type they use. Especially membership in a co-operative and practices of a business partner were mentioned as the reasons limiting this freedom of choice. The main business relations in both chains were described as having a long-term orientation and being based on formal written contracts. Typical for the main business relationships was also that they are not based on the existence of the key persons only; the relationship would remain even if the key people left the business. The quality of these relationships was satisfactory in both chains and across all the stakeholder groups, though the downstream processors and the retailers had a slightly more positive view on their main business partners than the farmers and the upstream processors. The businesses operating in the pig meat chain seemed also to be more dependent on their main business relations when compared to the businesses in the rye chain. Although the communication means were rather similar in both chains (the phone being the most important), there was some variation between the chains concerning the communication frequency necessary to maintain the relationship with the main business partner. In short, the businesses in the pig meat chain seemed to appreciate more frequent communication with their main business partners when compared to the businesses in the rye chain. Personal meetings with the main business partners were quite rare in both chains. All the respondent groups were, however, fairly satisfied with the communication frequency and information quality between them and the main business partner. The business cultures could be argued to be rather hegemonic among the businesses both in the pig meat and rye chains. Avoidance of uncertainty, appreciation of long-term orientation and independence were considered important factors in the business cultures. Furthermore, trust, commitment and satisfaction in business partners were thought to be essential elements of business operations in all the respondent groups. In order to investigate which factors have an effect on the choice of a relationship type, several hypotheses were tested by using binary and multinomial logit analyses. According to these analyses it could be argued that avoidance of uncertainty and risk has a certain effect on the relationship type chosen, i.e. the willingness to avoid uncertainty increases the probability to choose stable relationships, like repeated market transactions and formal written contracts, but not necessary those, which require high financial commitment (like financial participation arrangements). The probability of engaging in financial participation arrangements seemed to increase with long-term orientation. The hypotheses concerning the sustainability of the economic relations were tested by using structural equation model (SEM). In the model, five variables were found to have a positive and statistically significant impact on the sustainable economic relationship construct. Ordered relative to their importance, those factors are: (i) communication quality, (ii) personal bonds, (iii) equal power distribution, (iv) local embeddedness and (v) competition.

A Formalised Model of the Information and Materials Handling Activities in the Construction Process

A model of the information and material activities that comprise the overall construction process is presented, using the SADT activity modelling methodology. The basic model is further refined into a number of generic information handling activities such as creation of new information, information search and retrieval, information distribution and person-to-person communication. The viewpoint could be described as information logistics. This model is then combined with a more traditional building process model, consisting of phases such as design and construction. The resulting two-dimensional matrix can be used for positioning different types of generic IT-tools or construction specific applications. The model can thus provide a starting point for a discussion of the application of information and communication technology in construction and for measurements of the impacts of IT on the overall process and its related costs.

Information Technology in Construction – Domain Definition and Research Issues

This article discusses the scope of research on the application of information technology in construction (ITC). A model of the information and material activities which together constitute the construction process is presented, using the IDEF0 activity modelling methodology. Information technology is defined to include all kinds of technology used for the storage, transfer and manipulation of information, thus also including devices such as copying machines, faxes and mobile phones. Using the model the domain of ITC research is defined as the use of information technology to facilitate and re-engineer the information process component of construction. Developments during the last decades in IT use in construction is discussed against a background of a simplified model of generic information processing tasks. The scope of ITC is compared with the scopes of research in related areas such as design methodology, construction management and facilities management. Health care is proposed as an interesting alternative (to the often used car manufacturing industry), as an IT application domain to compare with. Some of the key areas of ITC research in recent years; expert systems, company IT strategies, and product modelling are shortly discussed. The article finishes with a short discussion of the problems of applying standard scientific methodology in ITC research, in particular in product model research.

Determinants and Consequences of Information Sharing with Key Suppliers

As companies become more efficient with respect to their internal processes, they begin to shift the focus beyond their corporate boundaries. Thus, the recent years have witnessed an increased interest by practitioners and researchers in interorganizational collaboration, which promises better firm performance through more effective supply chain management. It is no coincidence that this interest comes in parallel with the recent advancements in Information and Communication Technologies, which offer many new collaboration possibilities for companies. However, collaboration, or any other type of supply chain integration effort, relies heavily on information sharing. Hence, this study focuses on information sharing, in particular on the factors that determine it and on its value. The empirical evidence from Finnish and Swedish companies suggests that uncertainty (both demand and environmental) and dependency in terms of switching costs and asset specific investments are significant determinants of information sharing. Results also indicate that information sharing improves company performance regarding resource usage, output, and flexibility. However, companies share information more intensely at the operational rather than the strategic level. The use of supply chain practices and technologies is substantial but varies across the two countries. This study sheds light on a common trend in supply chains today. Whereas the results confirm the value of information sharing, the contingent factors help to explain why the intensity of information shared across companies differ. In the future, competitive pressures and uncertainty are likely to intensify. Therefore, companies may want to continue with their integration efforts by focusing on the determinants discussed in this study. However, at the same time, the possibility of opportunistic behavior by the exchange partner cannot be disregarded.

Guessing under source uncertainty with side information

We study the problem of guessing the realization of a finite alphabet source, when some side information is provided, in a setting where the only knowledge the guesser has about the source and the correlated side information is that the joint source is one among a family. We define a notion of redundancy, identify a quantity that measures this redundancy, and study its properties. We then identify good guessing strategies that minimize the supremum redundancy (over the family). The minimum value measures the richness of the uncertainty class.

Stability of scheduled message communication over degraded broadcast channels

We develop a multi-class discrete-time processor-sharing queueing model for scheduled message communication over a discrete memoryless degraded broadcast channel. The framework we consider here models both the random message arrivals and the subsequent reliable communication by suitably combining techniques from queueing theory and information theory. Requests for message transmissions are assumed to arrive according to i.i.d. arrival processes. Then, (i) we derive an outer bound to the stability region of message arrival rate vectors achievable by the class of stationary scheduling policies, (ii) we show for any message arrival rate vector that satisfies the outer bound, that there exists a stationary "state-independent" policy that results in a stable system for the corresponding message arrival processes, and (iii) under an asymptotic regime, we show that the stability region of information arrival rate vectors is the information-theoretic capacity region of a degraded broadcast channel.

A simple low-cost electrical switching analyzer for I-V characterization of switching samples and devices

The phenomena of nonlinear I-V behavior and electrical switching find extensive applications in power control, information storage, oscillators, etc. The study of I-V characteristics and switching parameters is necessary for the proper application of switching materials and devices. In the present work, a simple low-cost electrical switching analyzer has been developed for the measurement of the electrical characteristics of switching materials and devices. The system developed consists of a microcontroller-based excitation source and a high-speed data acquisition system. The design details of the excitation source, its interface with the high-speed data acquisition system and personal computer, and the details of the application software developed for automated measurements are described. Typical I-V characteristics and switching curves obtained with the system developed are also presented to illustrate the capability of the instrument developed.

Information Theoretic Results for Three-User Cognitive Channels

In this paper, we introduce the three-user cognitive radio channels with asymmetric transmitter cooperation, and derive achievable rate regions under several scenarios depending on the type of cooperation and decoding capability at the receivers. Two of the most natural cooperation mechanisms for the three-user channel are considered here: cumulative message sharing (CMS) and primary-only message sharing (PMS). In addition to the message sharing mechanism, the achievable rate region is critically dependent on the decoding capability at the receivers. Here, we consider two scenarios for the decoding capability, and derive an achievable rate region for each one of them by employing a combination of superposition and Gel'fand-Pinsker coding techniques. Finally, to provide a numerical example, we consider the Gaussian channel model to plot the rate regions. In terms of achievable rates, CMS turns out to be a better scheme than PMS. However, the practical aspects of implementing such message-sharing schemes remain to be investigated.

Joint Source-Channel Coding over a Fading Multiple Access Channel with Partial Channel State Information

In this paper we address the problem of transmission of correlated sources over a fast fading multiple access channel (MAC) with partial channel state information available at both the encoders and the decoder. We provide sufficient conditions for transmission with given distortions. Next these conditions are specialized to a Gaussian MAC (GMAC). We provide the optimal power allocation strategy and compare the strategy with various levels of channel state information.

Systems between information and knowledge : In a memory management model of an extended enterprise

The research question of this thesis was how knowledge can be managed with information systems. Information systems can support but not replace knowledge management. Systems can mainly store epistemic organisational knowledge included in content, and process data and information. Certain value can be achieved by adding communication technology to systems. All communication, however, can not be managed. A new layer between communication and manageable information was named as knowformation. Knowledge management literature was surveyed, together with information species from philosophy, physics, communication theory, and information system science. Positivism, post-positivism, and critical theory were studied, but knowformation in extended organisational memory seemed to be socially constructed. A memory management model of an extended enterprise (M3.exe) and knowformation concept were findings from iterative case studies, covering data, information and knowledge management systems. The cases varied from groups towards extended organisation. Systems were investigated, and administrators, users (knowledge workers) and managers interviewed. The model building required alternative sets of data, information and knowledge, instead of using the traditional pyramid. Also the explicit-tacit dichotomy was reconsidered. As human knowledge is the final aim of all data and information in the systems, the distinction between management of information vs. management of people was harmonised. Information systems were classified as the core of organisational memory. The content of the systems is in practice between communication and presentation. Firstly, the epistemic criterion of knowledge is not required neither in the knowledge management literature, nor from the content of the systems. Secondly, systems deal mostly with containers, and the knowledge management literature with applied knowledge. Also the construction of reality based on the system content and communication supports the knowformation concept. Knowformation belongs to memory management model of an extended enterprise (M3.exe) that is divided into horizontal and vertical key dimensions. Vertically, processes deal with content that can be managed, whereas communication can be supported, mainly by infrastructure. Horizontally, the right hand side of the model contains systems, and the left hand side content, which should be independent from each other. A strategy based on the model was defined.

The Relay Selection and Transmission Trade-off in Cooperative Communication Systems

A common and practical paradigm in cooperative communication systems is the use of a dynamically selected `best' relay to decode and forward information from a source to a destination. Such systems use two phases - a relay selection phase, in which the system uses transmission time and energy to select the best relay, and a data transmission phase, in which it uses the spatial diversity benefits of selection to transmit data. In this paper, we derive closed-form expressions for the overall throughput and energy consumption, and study the time and energy trade-off between the selection and data transmission phases. To this end, we analyze a baseline non-adaptive system and several adaptive systems that adapt the selection phase, relay transmission power, or transmission time. Our results show that while selection yields significant benefits, the selection phase's time and energy overhead can be significant. In fact, at the optimal point, the selection can be far from perfect, and depends on the number of relays and the mode of adaptation. The results also provide guidelines about the optimal system operating point for different modes of adaptation. The analysis also sheds new insights on the fast splitting-based algorithm considered in this paper for relay selection.

Electrostatic Field Analysis of Electrooptic Devices

We describe a Finite Difference Method for the determination of the electrostatic field in a multilayered electrooptic device. The Laplace equation is solved, assuming a suitable closed area, by taking into account the different permittivities of the various layers. The effect of a higher permittivity in the guiding layer has been explicitly considered. As a practical example, we calculate the phase shift of a guided optical wave within an electrooptic modulator. A review of the various methods in use for the field analysis is given. Some criteria for the selection of the appropriate method are also mentioned.

Promoting the European Union : Attitudinal stance adjectives in three genres of EU communication to the public

Målet för Pro Gradu-avhandlingen är att undersöka hur Europeiska unionen (EU) marknadsförs genom användningen av värderande adjektiv i tre genrer av skriftlig kommunikation från EU till medlemsstaternas medborgare. Undersökningen är inriktad på tre forskningsfrågor: hur marknadsföringen av EU syns i användningen av värderande adjektiv i de tre genrerna, vilka de centrala skillnaderna mellan de tre genrerna är gällande användningen av värderande adjektiv, samt på vilket sätt texterna uppfyller sitt kommunikativa syfte, nämligen att informera allmänheten om EU:s verksamhet och marknadsföra EU som en giltig och handlingskraftig union. Den teoretiska ramen för undersökningen grundar sig på genreanalys, kommunikationsteori och teorier om hur författarens värdering (stance) syns i texter. Skillnaden mellan genre, texttyp och register diskuteras, och teoridelen redogör även för begreppet diskurssamfund, dvs. den grupp personer som i ett yrkesmässigt eller institutionellt sammanhang producerar och använder sig av en genre enligt dess kommunikativa konventioner. Materialet behandlas även utgående från Egon Werlichs indelning av texttyper i deskriptiva, narrativa, expositära, argumentativa och instruktiva texter. Materialet består av tre delar som representerar var sin genre: informationsbroschyrer, pressmeddelanden och den Allmänna rapporten om Europeiska unionens verksamhet, som utges av EU varje år. Storleken på varje del av materialet varierar mellan 20 000 - 30 000 ord. Materialet har valts på basis av de teman texterna behandlar, och kriterierna för urvalet är bl.a. att texterna behandlar ämnen som har anknytning till medborgarnas vardag, att de är riktade till allmänheten, och att de finns tillgängliga på Internet. Undersökningen är genomförd som en kvalitativ genreanalys. Materialet analyseras först utgående från kontexten och det samhälleliga sammanhanget enligt Vijay K. Bhatias metodik för analys av obekanta genrer. Det kommunikativa syftet, författaren och den tilltänkta läsarkretsen, dvs. målgruppen för kommunikationen, fastställs. Värderande adjektiv som uttrycker författarens hållning har plockats ur texten manuellt och med hjälp av konkordansprogrammet AntConc, och placerats i 16 kategorier enligt de värden de uttrycker. Varje genre analyseras sedan språkligt med utgångspunkt i adjektivlistorna, varefter resultaten jämförs med varandra. Undersökningen visar att pressmeddelandena innehåller det största antalet värderande adjektiv, medan informationsbroschyrerna innehåller det minsta antalet värderande adjektiv. Den Allmänna rapporten om Europeiska unionens verksamhet innehåller delar med tätt förekommande värderande adjektiv, i synnerhet i stycken som behandlar mer kontroversiella ämnen. I alla tre genrer sammanfaller ett högt antal värderande adjektiv med argumentativ text, och argumentativ text förekommer främst då ämnet som diskuteras rör sig på en mer abstrakt nivå, t.ex. om EU:s värderingar och grundläggande principer, eller då texten behandlar sådan politik som delar allmänhetens uppfattning. För EU utgör alla tre genrer viktiga kanaler för kommunikationen till medlemsstaternas medborgare, och EU kan genom sitt informationsmaterial och sina officiella publikationer informera om, förklara och marknadsföra sin verksamhet på ett sätt som avser att upprätthålla och förbättra EU:s image. Utarbetandet av lämpliga texter är ändå krävande på grund av den heterogena målgruppen, och det är en utmaning i sig att få fram rätt budskap bland det stora utbudet information som finns tillgängligt på Internet.