Space–Time Block Codes and the Complexity of Sphere Decoding

In wireless communications the transmitted signals may be affected by noise. The receiver must decode the received message, which can be mathematically modelled as a search for the closest lattice point to a given vector. This problem is known to be NP-hard in general, but for communications applications there exist algorithms that, for a certain range of system parameters, offer polynomial expected complexity. The purpose of the thesis is to study the sphere decoding algorithm introduced in the article On Maximum-Likelihood Detection and the Search for the Closest Lattice Point, which was published by M.O. Damen, H. El Gamal and G. Caire in 2003. We concentrate especially on its computational complexity when used in space–time coding. Computer simulations are used to study how different system parameters affect the computational complexity of the algorithm. The aim is to find ways to improve the algorithm from the complexity point of view. The main contribution of the thesis is the construction of two new modifications to the sphere decoding algorithm, which are shown to perform faster than the original algorithm within a range of system parameters.

Design and Analysis of Forward Error Control Coding and Signaling for Guaranteeing QoS in Wireless Broadcast Systems

Broadcasting systems are networks where the transmission is received by several terminals. Generally broadcast receivers are passive devices in the network, meaning that they do not interact with the transmitter. Providing a certain Quality of Service (QoS) for the receivers in heterogeneous reception environment with no feedback is not an easy task. Forward error control coding can be used for protection against transmission errors to enhance the QoS for broadcast services. For good performance in terrestrial wireless networks, diversity should be utilized. The diversity is utilized by application of interleaving together with the forward error correction codes. In this dissertation the design and analysis of forward error control and control signalling for providing QoS in wireless broadcasting systems are studied. Control signaling is used in broadcasting networks to give the receiver necessary information on how to connect to the network itself and how to receive the services that are being transmitted. Usually control signalling is considered to be transmitted through a dedicated path in the systems. Therefore, the relationship of the signaling and service data paths should be considered early in the design phase. Modeling and simulations are used in the case studies of this dissertation to study this relationship. This dissertation begins with a survey on the broadcasting environment and mechanisms for providing QoS therein. Then case studies present analysis and design of such mechanisms in real systems. The mechanisms for providing QoS considering signaling and service data paths and their relationship at the DVB-H link layer are analyzed as the first case study. In particular the performance of different service data decoding mechanisms and optimal signaling transmission parameter selection are presented. The second case study investigates the design of signaling and service data paths for the more modern DVB-T2 physical layer. Furthermore, by comparing the performances of the signaling and service data paths by simulations, configuration guidelines for the DVB-T2 physical layer signaling are given. The presented guidelines can prove useful when configuring DVB-T2 transmission networks. Finally, recommendations for the design of data and signalling paths are given based on findings from the case studies. The requirements for the signaling design should be derived from the requirements for the main services. Generally, these requirements for signaling should be more demanding as the signaling is the enabler for service reception.

Complexity Optimization in Product Development with Modularization

A company’s competence to manage its product portfolio complexity is becoming critically important in the rapidly changing business environment. The continuous evolvement of customer needs, the competitive market environment and internal product development lead to increasing complexity in product portfolios. The companies that manage the complexity in product development are more profitable in the long run. The complexity derives from product development and management processes where the new product variant development is not managed efficiently. Complexity is managed with modularization which is a method that divides the product structure into modules. In modularization, it is essential to take into account the trade-off between the perceived customer value and the module or component commonality across the products. Another goal is to enable the product configuration to be more flexible. The benefits are achieved through optimizing complexity in module offering and deriving the new product variants more flexibly and accurately. The developed modularization process includes the process steps for preparation, mapping the current situation, the creation of a modular strategy and implementing the strategy. Also the organization and support systems have to be adapted to follow-up targets and to execute modularization in practice.

Overcoming the Complexity of Software Product Management

This thesis describes an approach to overcoming the complexity of software product management (SPM) and consists of several studies that investigate the activities and roles in product management, as well as issues related to the adoption of software product management. The thesis focuses on organizations that have started the adoption of SPM but faced difficulties due to its complexity and fuzziness and suggests the frameworks for overcoming these challenges using the principles of decomposition and iterative improvements. The research process consisted of three phases, each of which provided complementary results and empirical observation to the problem of overcoming the complexity of SPM. Overall, product management processes and practices in 13 companies were studied and analysed. Moreover, additional data was collected with a survey conducted worldwide. The collected data were analysed using the grounded theory (GT) to identify the possible ways to overcome the complexity of SPM. Complementary research methods, like elements of the Theory of Constraints were used for deeper data analysis. The results of the thesis indicate that the decomposition of SPM activities depending on the specific characteristics of companies and roles is a useful approach for simplifying the existing SPM frameworks. Companies would benefit from the results by adopting SPM activities more efficiently and effectively and spending fewer resources on its adoption by concentrating on the most important SPM activities.

Species och artikelbruk i finskspråkiga grundskoleelevers inlärarsvenska. En longitudinell undersökning i årskurserna 7–9

Denna doktorsavhandling utreder hur finska grundskolelever använder de svenska substantivens bestämdhetsformer och artiklar och hur deras kunskaper utvecklas under årskurserna 7-9. Species och artikelbruk är problematiska för alla andraspråksinlärare i svenska, men de är synnerligen svåra för inlärare vars förstaspråk saknar morfologisk species. Det svenska systemet avviker också kraftigt från det motsvarande systemet i engelskan, varför tidigare kunskaper i engelska inte är till någon stor hjälp i inlärningen, låt vara att bestämdheten som begrepp redan är bekant för inläraren. Den teoretiska referensramen bygger på både grammatiska beskrivningar av den svenska grammatiken och på teorierna om grammatikinlärningen i andraspråk. Bland de sistnämnda är teorierna om tvärspråkligt inflytande, explicit respektive implicit inlärning samt helsekvensinlärning (på engelska formulaic language) av relevans. Undersökningsmaterialet består av korta texter samt inspelat muntligt material som med jämna mellanrum insamlats av finskspråkiga grundskolelever (n=67) som läser B-svenska. Undersökningen är i första hand kvantitativ, om än inmatningen av nominalfraserna i materialet samt deras formella och semantiska aspekter i analysprogrammet Microsoft Access också innebar en omfattande kvalitativ analys. Undersökningen bygger på performansanalysen och analysen av obligatoriska kontexter och beräkningen av frekvenser och korrekthetsprocent för de olika nominalfrastyperna. Informanterna använder komplext språk redan i årskurs 7. Korrekthetsprocenten stiger under undersökningstiden i de flesta frastyperna, men skillnaderna är sällan statistiskt signifikanta. Den normativa analysen visar också, att formfelen är i både det skriftliga och det muntliga materialet signifikant vanligare än speciesfelen. Det är med andra ord lättare för informanterna att välja rätt species än att bilda en korrekt nominalfras. I tidigare undersökningar i Sverige har likadana resultat nåtts. De mest centrala frastyperna i undersökningen bildar i båda typerna av materialet en inlärningsgång som upprepas i alla årskurser och kan förklaras med komplexitetsskillnaderna mellan de olika frastyperna. Informanterna behärskar bäst de frastyper, som varken innehåller artiklar eller ändelser. Näst bäst behärskar de substantivets bestämda form singularis och svagast obestämd form singularis, vars artikel är en klassisk svårighetskälla för finska svenskinlärare. Analysen av informanternas läromedel visar dock att den typiska undervisningsordningen i läromedlen inte motsvarar inlärningsgången som upptäckts i denna undersökning.

Chromatoid body mediated RNA regulation in mouse male germline

Male germ cell differentiation, spermatogenesis is an exceptional developmental process that produces a massive amount of genetically unique spermatozoa. The complexity of this process along with the technical limitations in the germline research has left many aspects of spermatogenesis poorly understood. Post-meiotic haploid round spermatids possess the most complex transcriptomes of the whole body. Correspondingly, efficient and accurate control mechanisms are necessary to deal with the huge diversity of transcribed RNAs in these cells. The high transcriptional activity in round spermatids is accompanied by the presence of an uncommonly large cytoplasmic ribonucleoprotein granule, called the chromatoid body (CB) that is conjectured to participate in the RNA post-transcriptional regulation. However, very little is known about the possible mechanisms of the CB function. The development of a procedure to isolate CBs from mouse testes was this study’s objective. Anti-MVH immunoprecipitation of cross-linked CBs from a fractionated testicular cell lysate was optimized to yield considerable quantities of pure and intact CBs from mice testes. This protocol produced reliable and reproducible data from the subsequent analysis of CB’s protein and RNA components. We found that the majority of the CB’s proteome consists of RNA-binding proteins that associate functionally with different pathways. We also demonstrated notable localization patterns of one of the CB transient components, SAM68 and showed that its ablation does not change the general composition or structure of the CB. CB-associated RNA analysis revealed a strong accumulation of PIWI-interacting RNAs (piRNAs), mRNAs and long non-coding RNAs (lncRNAs) in the CB. When the CB transcriptome and proteome analysis results were combined, the most pronounced molecular functions in the CB were related to piRNA pathway, RNA post-transcriptional processing and CB structural scaffolding. In addition, we demonstrated that the CB is a target for the main RNA flux from the nucleus throughout all steps of round spermatid development. Moreover, we provided preliminary evidence that those isolated CBs slice target RNAs in vitro in an ATPdependent manner. Altogether, these results make a strong suggestion that the CB functions involve RNA-related and RNA-mediated mechanisms. All the existing data supports the hypothesis that the CB coordinates the highly complex haploid transcriptome during the preparation of the male gametes for fertilization. Thereby, this study provides a fundamental basis for the future functional analyses of ribonucleoprotein granules and offers also important insights into the mechanisms governing male fertility.