Jerry Eriksson

Real-time video over wireless ad-hoc networks

In this paper we investigate important issue for real-time video over wireless ad-hoc networks on different layers. Many error control methods for this approach use multiple streams and multipath routing. Thus the new proactive, link-state routing protocol have been developed, where the protocol finds the available route in the network and also it will not cause any interruption in the video traffic between the source and the destination. The open source MPEG-4 is also implemented to get the efficient video quality for the picture.

A parallel interval method implementation for global optimization using dynamic load balancing

During the past few years the interest paid to global optimization has rapidly increased. One of the main reasons is the new technology of parallel computers which offer computational power capable of solving global optimization problems in reasonable time. The method studied in this work is based on interval analysis which provides a reliable way for solving the problem. Despite the fact that the method contains a high degree of potential parallelism, it is not straight forward to parallelize due to its irregular and unpredictable computational behaviour. This paper deals with the problem of balancing the load dynamically, both with respect to the quantity and to the quality of the tasks. Efficient strategies are proposed and implemented on an Intel iPSC/2 hypercube. Since the sequential algorithm is used as a base it will be modified to suit the parallel algorithm.AbstractВ течение ностедних нескольких пег ннтерес к нроблеме глобальной онтимнзанин быстро возрастал. Олна нз основных врнчин этого — нобые технологии параллельных компьютеров, обеспечнваюппе аостаточвую вычнслительную мощность для решения залач глоза глобальной онтнмизации за разумное время. Мегол, рассмотренный в данной работе, оснонан на интервальном анализе, которьй овеснечивает надежный нуть решения залачи. Несмотря на значительную до←ю нотенниадьного параллелизма в зтом метоле, его параллелизация ирелставляет собой хетрнвиальную залачу нз-за нерегулярного и непрелсказуемого хола вычислений. Настоящая рабога рассматривает проб←ему динамического балаисирования иагрузки с учетом как качества, так и количества залач. Преллаіаются зффектнiвные стратетии решения в оиисывается их реализация на гинеркуве Intel iPSC/2. ПосколЧjку в качестве вiсходного исиользуется нонользуется иослеловательный алгоритм, он будет модифниирован, что нозводит всхользовать ето как иараллельный.

Early multicast collision detection in CSMA/CA networks

Reliable multicast is especially difficult to achieve in IEEE 802.11 CSMA/CA networks when a large number of unicast stations are contending with the multicast transmissions. Motivated by capacity problems in a sports infotainment product the authors developed early multicast collision detection (EMCD) specifically tailored to accommodate a large number of legacy terminals in multiple overlapping cells. The algorithm is based on the fact that in the absence of hidden terminals two stations must start their transmissions simultaneously to cause a collision. A station using EMCD introduces an early pause in the multicast transmission, performs a clear channel assessment (CCA), and if another sender is detected, schedules a retransmission. We have evaluated our method using simulations. Results show that EMCD increases the multicast reliability even at relatively moderate network loads.

A Nonlinear Iterative Reconstruction and Analysis Approach to Shape-Based Approximate Electromagnetic Tomography

A nonlinear Helmholtz-equation-modeled electromagnetic tomographic reconstruction problem is solved for the object boundary and inhomogeneity parameters in a damped Tikhonov-regularized Gauss-Newton (DTRGN) solution framework. In this paper, the object is represented in a suitable global basis, whereas the boundary is expressed as the zero level set of a signed-distance function. For an explicit parameterized boundary-representation-based reconstruction scheme, analytical Jacobian and Hessian calculations are made to express the changes in scattered field values w.r.t. changes in the inhomogeneity parameters and the control points in a spline representation of the object boundary, via the use of a level-set representation of the object. Even though, in this paper, a homogeneous dielectric is considered and a spline representation has been used to represent the boundary, the formulation can be used for a general global basis representation of the inhomogeneity as well as arbitrary parameterizations of the boundary, and is generalizable to three dimensions. Reconstruction results are presented for test cases of landminelike dielectric objects embedded in the ground under noisy data conditions. To confirm convergence and, at times, to know which of the obtained iterates are closer to the actual unknown solution, using a perturbation theory framework, a local (Hessian-based) convergence analysis is applied to the DTRGN scheme for the reconstruction, yielding estimates of convergence rates in the residual and parameter spaces.

An implicit radial basis function based reconstruction approach to electromagnetic shape tomography

In a reconstruction problem for subsurface tomography (modeled by the Helmholtz equation), we formulate a novel reconstruction scheme for shape and electromagnetic parameters from scattered field d ...

Local results for the Gauss-Newton method on constrained rank-deficient nonlinear least squares

A nonlinear least squares problem with nonlinear constraints may be ill posed or even rank-deficient in two ways. Considering the problem formulated as

Regularization tools for training large feed-forward neural networks using automatic differentiation

min_{x} 1/2Vert f_{2}(x) Vert _{2}^{2}

A collision detection method for multicast transmissions in CSMA/CA networks

subject to the constraints

Truncated Gauss–Newton algorithms for Ill-conditioned nonlinear least squares problems

f_{1}(x) = 0

Quasi-Newton Methods for Nonlinear Least Squares Focusing on Curvatures

, the Jacobian