Search for dissertations about: "factor graphs"

Showing result 1 - 5 of 14 swedish dissertations containing the words factor graphs.

2. 1. Towards the Limits of Nonlinearity Compensation for Fiber-Optic Channels

   Author : Naga Vishnukanth Irukulapati; Chalmers tekniska högskola; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Viterbi algorithm; fiber-optic channel; stochastic digital backpropagation; performance limits; factor graphs; near-MAP detector; Digital backpropagation; nonlinear compensation; mutual information;

   Abstract : The performance of long-haul coherent optical systems is fundamentally limited by fiber nonlinearity and its interplay with chromatic dispersion and noise. Due to nonlinearity, the signal propagating through the fiber interacts with itself and with the noise generated from the inline amplifiers. READ MORE

4. 2. On Nonlinear Compensation Techniques for Coherent Fiber-Optical Channel

   Author : Naga Vishnukanth Irukulapati; Chalmers tekniska högskola; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; performance limits.; nonlinear compensation; factor graphs; fiber-optical communications; near-MAP detector; Digital backpropagation;

   Abstract : Fiber-optical communication systems form the backbone of the internet, enabling global broadband data services. Over the past decades, the demand for high-speed communications has grown exponentially. One of the key techniques for the efficient use of existing bandwidth is the use of higher order modulation formats along with coherent detection. READ MORE

5. 3. Serially Concatenated Space-Time Coded Continuous Phase Modulation

   Author : Dhammika Bokolamulla; Chalmers tekniska högskola; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; serially concatenated codes; symbol-by-symbol {MAP} detection; factor graphs; sum-product algorithm; Iterative detection; multiuser detection; space-time codes; continuous phase modulation;

   Abstract : Certain problems associated with reliable digital wireless communication over a frequency-flat slow Rayleigh fadingchannel are treated, when the transmitted signal is modulated using continuous phase modulation (CPM) due to the desirable properties of CPM. The primary focus of attention is on detection strategies, and the thesis proposes iterative detection algorithms for CPM signals transmitted over frequency-flat slow Rayleigh fading channels. READ MORE

6. 4. Hardness of Approximating Constraint Satisfaction Problems and Their Variants in Presence of Additional Structural Assumptions

   Author : Aleksa Stankovic; Johan Håstad; Per Austrin; Luca Trevisan; KTH; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Hardness of Approximation; Approximation Algorithms; Label Cover; Vertex Cover; Unique Games Conjecture; Max-3-Lin; Universal Factor Graphs; Regular Constraint Satisfaction Problems; Inapproximerbarhet; Approximationsalgoritm; Label Cover; Vertex Cover; Unique Games Conjecture; Max-3-Lin; Universell Faktorgraf; Regelbundna Begränsningsproblem; Datalogi; Computer Science;

   Abstract : This thesis studies how the approximability of some fundamental computational problems is affected by some additional requirements on the structure of the inputs. The problems studied in this thesis belong or are closely related to constraint satisfaction problems (CSPs), which are considered to be one of the most fundamental problems in theoretical computer science. READ MORE

7. 5. Analytical and Iterative Methods of Computing PageRank of Networks

   Author : Pitos Seleka Biganda; Sergei Silvestrov; Christopher Engström; Dmitrii Silvestrov; Anatoliy Malyarenko; Milica Rancic; Oleg Seleznjev; Mälardalens högskola; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Mathematics Applied Mathematics; matematik tillämpad matematik;

   Abstract : This thesis is about variants of PageRank, methods of PageRank computation and perturbation analysis of a PageRank vector as a stationary distribution of a kind of perturbed Markov chain model. Chapter 2 of this thesis gives closed form formulae for ordinary and lazy PageRanks for some specific simple line graphs. READ MORE