In this thesis, a blind symbol timing synchronization algorithm based on cyclic prefix for OFDM systems in multipath fading channels is proposed. It finds the starting point of symbol timing for using appropriate weights which are designed from channel delay spread characteristics. In multipath fading channels, the conventional ML (maximum likelihood) algorithm estimate is biased and has a large variance due to the effect of channel delay spread. The proposed exponential weighting methods not only solve the above problems but also improve the accuracy of symbol timing. Particularly, the proposed method does not require the information of SNR and channel length. From computer simulation results, the proposed method outperforms the other conventional algorithms and is also robust against the effect of multipath fading channels.

<p>Syftet med mitt examensarbete var att ta reda på hur läromedel i matematik för år 4-6 tar upp kunskapen om prefixen kring vikt, längd och volym och vilka kunskaper elever i år 6 har i ämnet.</p><p>Jag har analyserat fem olika läromedel och gjort en enkätundersökning i fem klasser. Genom min undersökning har jag kommit fram till att läromedlen ger eleverna för få tillfällen att praktiskt erfara kunskaper om de olika enheterna. De flesta informerar om vad prefixen betyder men det förekommer inga arbetsuppgifter där eleverna får lära och förstå sammanhanget och nyttan med att kunna dem. Resultatet av min enkätundersökning visade att många elever vet vad enheterna för längd, vikt och volym heter, men har dåliga kunskaper i vad prefixen betyder och svårigheter med att omvandla enheterna. I slutet av mitt examensarbete ger jag några förslag på hur undervisningen kan läggas upp för att ge eleverna större möjlighet att förstå prefixens betydelse och nyttan med kunskapen.</p>

The Internet has become an indispensable resource for today's society. It is at the center of the today's business, entertainment, and social world. However, the core of our identities on the Internet, the IP addresses that are used to send and receive data throughout the Internet, are insecure. Attackers today are able to send data purporting to be from nearly any location (IP spoofing) and to reroute data destined for victims to the attackers themselves (IP prefix hijacking). Victims of these attacks may experience denial of service, misplaced blame, and theft of their traffic. These attacks are of the utmost importance since they affect the core layer of the Internet. Although the mechanisms of the attacks are different, they are essentially different sides of the same coin; spoofing attacks forge the identity of the sender, while hijacking attacks forge the identity of the receiver. They revolve around the same underlying lack of a secure identity on the Internet. This research reviews the existing state of the art IP spoofing and IP prefix hijacking research and proposes new defenses to close the missing gaps and provide a new level of security to our identities on the Internet. This material is based upon work supported by the National Science Foundation under Grants No. CNS-0520326 and CNS-1118101. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. This dissertation includes both previously published/unpublished and co-authored material.

The Border Gateway Protocol (BGP), the main component of core Internet connectivity, suffers vulnerability issues related to the impersonation of the ownership of IP prefixes for Autonomous Systems (ASes). In this context, a number of studies have focused on securing the BGP through several techniques, such as monitoring-based, historical-based and statistical-based behavioural models. In spite of the significant research undertaken, the proposed solutions cannot detect the IP prefix hijack accurately or even differentiate it from other types of attacks that could threaten the performance of the BGP. This research proposes three novel detection methods aimed at tracking the behaviour of BGP edge routers and detecting IP prefix hijacks based on statistical analysis of variance, the attack signature approach and a classification-based technique. The first detection method uses statistical analysis of variance to identify hijacking behaviour through the normal operation of routing information being exchanged among routers and their behaviour during the occurrence of IP prefix hijacking. However, this method failed to find any indication of IP prefix hijacking because of the difficulty of having raw BGP data hijacking-free. The research also proposes another detection method that parses BGP advertisements (announcements) and checks whether IP prefixes are announced or advertised by more than one AS. If so, events are selected for further validation using Regional Internet Registry (RIR) databases to determine whether the ASes announcing the prefixes are owned by the same organisation or different organisations. Advertisements for the same IP prefix made by ASes owned by different organisations are subsequently identified as hijacking events. The proposed algorithm of the detection method was validated using the 2008 YouTube Pakistan hijack event; the analysis demonstrates that the algorithm qualitatively increases the accuracy of detecting IP prefix hijacks. The algorithm is very accurate as long as the RIRs (Regional Internet Registries) are updated concurrently with hijacking detection. The detection method and can be integrated and work with BGP routers separately. Another detection method is proposed to detect IP prefix hijacking using a combination of signature-based (parsing-based) and classification-based techniques. The parsing technique is used as a pre-processing phase before the classification-based method. Some features are extracted based on the connectivity behaviour of the suspicious ASes given by the parsing technique. In other words, this detection method tracks the behaviour of the suspicious ASes and follows up with an analysis of their interaction with directly and indirectly connected neighbours based on a set of features extracted from the ASPATH information about the suspicious ASes. Before sending the extracted feature values to the best five classifiers that can work with the specifications of an implemented classification dataset, the detection method computes the similarity between benign and malicious behaviours to determine to what extent the classifiers can distinguish suspicious behaviour from benign behaviour and then detect the hijacking. Evaluation tests of the proposed algorithm demonstrated that the detection method was able to detect the hijacks with 96% accuracy and can be integrated and work with BGP routers separately.

In XML databases, the indexing process is based on a labelling or numbering scheme and generally used to label an XML document to perform an XML query using the path node information. Moreover, a labelling scheme helps to capture the structural relationships during the processing of queries without the need to access the physical document. Two of the main problems for labelling XML schemes are duplicated labels and the cost efficiency of labelling time and size. This research presents a novel dynamic XML labelling scheme, called the Pentagonal labelling scheme, in which data are represented as ordered XML nodes with relationships between them. The update of these nodes from large scale XML documents has been widely investigated and represents a challenging research problem as it means relabelling a whole tree. Our algorithms provide an efficient dynamic XML labelling scheme that supports data updates without duplicating labels or relabelling old nodes. Our work evaluates the labelling process in terms of size and time, and evaluates the labelling scheme’s ability to handle several insertions in XML documents. The findings indicate that the Pentagonal scheme shows a better initial labelling time performance than the compared schemes, particularly when using large XML datasets. Moreover, it efficiently supports random skewed updates, has fast calculations and uncomplicated implementations so efficiently handles updates. Also, it proved its capability in terms of the query performance and in determining the relationships. / Libyan government

När det stod klart att antalet adresser i ipv4 inte skulle räcka, togs ipv6 fram. Med nya funktioner som hade anpassats till den infrastruktur som hade byggts upp världen runt så fanns det nu en ersättare till ipv4. Men skillnaderna är stora och protokollen är i sig inte lika varandra alls, framför allt inte när man tittar på inbygda funktioner. En av dessa nya funktioner i ipv6 är det som kallas för Prefix delegation, ett enkelt och smidigt sätt att per automatik dela ut delar av ett större nät till mindre nät. Även om det finns enkla och smidiga sätt att genomföra detta på så är inte all infrastuktur så enkel. Det gör att denna typ av funktioner kommer varvas med routes, både statiska och dynamiska. För att få en förståelse för hur detta kan skilja sig åt har vi tittat på en översikt av hur infrastrukturen kan se ut och sedan testat hur man skulle kunna lösa adresseringen genom en automatiserad process och en statisk process. Resultatet visar att den automatiserade lösningen kräver lite mer förarbete och specificerad utrustning, men att arbetet därefter blir lätt att kontrollera, felsöka och dokumentera. Den statiska processen är mer rakt på sak och kräver ingen speciell utrustning, däremot kommer det bli svårt att kontrollera, felsöka och dokumentera då minsta förändring kan kräva mycket arbete där risken för komplikationer är stor. / When it became clear that the number of ipv4 addresses would not be enough, ipv6 was developed. With new features that had been adapted to the infrastructure that had been built up around the world, there was now a replacement for ipv4. But the differences are many and the protocols are not alike at all, especially when looking at the built-in functions. One of these new features in ipv6 is called Prefix Delegation, a simple and convenient way to automatically distribute parts of a larger network into smaller networks. Although there are simple and flexible way to implement this, the existing infrastructure of the Internet may not be so simple. The complexity of the infrastructure forces us to use a variety of routes, both static and dynamic. To get an understanding of how this can differ, we looked at an overview of how the infrastructure might look like and then tested how to solve the addressing through an automated process and a static process. The results shows that the automated solution requires a little more preparation and specified equipment, but the work then becomes easy to control, debug, and document. The static process is more straightforward and requires no special equipment, however, it will be difficult to control, debug, and document where the slightest change can require a lot of work where the risk of complications is great.

Det övergripande syftet med undersökningen har varit att studera etableringen och användningen av morfemet jätte i skrivna elevtexter och tidningstexter idag, med fokus på jätte som förstärkande prefix. Frågeställningen lyder: ”Hur, av vem och i vilken utsträckning används morfemet jätte i elevtexter och tidningstexter?”.För att besvara ovanstående har två korpusundersökningar genomförts, en på tidningstexter och en på elevtexter. Resultatet visar att jätte förekommer i relativt stor utsträckning jämfört med andra förstärkande prefix som till exempel tok- och super-. Vanligast är att jätte används i sammansättningar med adjektiv, både i tidningstexterna och elevtexterna. I tidningstexter förekommer det oftast vid direkt talspråksåtergivning men det har också tagit sig in i mer formella delar såsom ledare. I elevtexterna används jätte oftast vid berättande inslag. När jätte förekommer i sin grundform används det aldrig i betydelsen ”en övernaturlig varelse”.Språkbrukarna i tidningstexterna kan delas in i två grupper, intervjuade och journalister. Spridningen bland användarna är stor då det används av både kvinnor och män i olika åldrar och med olika yrken. I elevtexterna används jätte främst av flickor. Jätte används också inom flera olika ämnesområden men är något vanligare inom sport- och nöjesjournalistiken. Den breda användningen av jätte tyder på en språklig förändring där jätte nu är accepterat i skriftspråket, det används dock fortfarande främst i mer informella sammanhang. / The aim of this study has been to see the conventionalisation and use of the Swedish word jätte (giant) in newspapers and texts written by pupils in the Upper Secondary School, primarily when used as an intensifier in compound words. The question forming the basis of the study is: “How, by whom and to what extent is jätte used in newspapers and texts written by pupils?”To answer the question two corpora have been analysed. The results show that jätte is quite common compared to other Swedish intensifiers as “tok” and “super”. Usually it is used together with adjectives. When used in newspapers it is most commonly used in direct speech, but it is also used in more formal parts of the paper as the editorial. In the texts written by the pupils it is mostly used in sections with narrative elements.The people who use jätte in newspapers can be divided into two groups, journalists and interviewees. The word is widely spread among people and it is used by both women and men of different ages and with different socio-economical backgrounds. Among the pupils it is mostly used by girls. The word is used in different subject areas, although it is more common in sports and entertainment. The wide range of subjects and users indicate that the word is accepted to use in the written language, although it is more common in informal contexts.

Den här studien undersöker det ryska verbprefixet v(o)- och cirkumfixet v(o)- -sja i det konkreta fysiska rummet. Syftet med den kontrastiva studien är att undersöka och beskriva betydelser. Tvåspråkig data från en samtida rysk-svensk ordbok analyseras med Krongauz metod. En lista över verbaffixens betydelser byggs upp genom att jämföra lexikala betydelser och morfosyntaktiska konstruktioner för verben i båda språken. Resultatet visar att affixens betydelser kan delas in i följande kategorier: Spatiala rörelser in i ett slutet rum, Spatiala rörelser till en avgränsad yta, Spatiala rörelser mot en närhet, Vidhäftning och Platser i det fysiska rummet. / This present study investigates the Russian verbal prefix v(o)- and circumfix v(o)- -sja in the concrete physical space. The aim of the contrastive study is to explore and describe meanings. Bilingual data, extracted from a contemporary Russian-Swedish dictionary, is analysed by using Krongauz’s method. A list of meanings of the Russian verbal affixes is built by comparing similarities and differences between lexical meanings and morphosyntactic structures for the verbs in both languages. The result shows that the meanings of the affixes can be divided into the following categories: Spatial movements into an enclosed space, Spatial movements onto a delimited surface, Spatial movements towards a vicinity, Adhesion and Locations in physical space.

This thesis deals with the Longest Prefix Matching (LPM), which is a time-critical operation in packet forwarding. To achieve 100Gbps throughput, this operation has to be implemented in hardware and a forwarding table has to fit into the on-chip memory, which is limited by its small size. Current LPM algorithms need large memory to store IPv6 forwarding tables or cannot be simply implemented in HW. Therefore we performed an analysis of available IPv6 forwarding tables and several LPM algorithms. Based on this analysis, we propose a new algorithm which is able to provide very low memory demands for IPv4/IPv6 lookups. To the best of our knowledge, the proposed algorithm has the lowest memory requirements in comparison to existing LPM algorithms. Moreover, the proposed algorithm is suitable for IP lookup in 100Gbps networks, which is shown on new pipelined hardware architecture with 140Gbps throughput.

The diploma thesis deals with negation in Spanish, especially lexical negation and negative prefixes. It is divided into two parts: the first one is theoretical which is followed by a practical one, which contains its own research. The aim of the first part is to genereally define negation from the perspective of various disciplines and to characterize the means that are used to create the negative (in Spanish and Czech). The greatest emphasis is placed on word- formation negation, that is why basic word-forming processes are defined here. In the theoretical part, the greatest attention is paid to prefixation: basic categories of prefixes are described with emphasis on negative prefixes. The second part focuses on the research which is based on the work with the language corpus and subsequently the questionnaire, which was created for the purpose of the work. The aim of the practical part is to discover some specifics in the behaviour of individual negative prefixes (a-, des-, in-, anti- and contra-) and their possible interchangeability. Subsequently conclusions are drawn from this part, following the theoretical part and completing the overall view of lexical negation in Spanish.