Showing papers by "Vahab Mirrokni published in 2002"

Fault-tolerant and 3-dimensional distributed topology control algorithms in wireless multi-hop networks

Abstract: We can control the topology of a multi-hop wireless network by varying the transmission power at each node. The life-time of such networks depends on battery power at each node. This paper presents a distributed fault-tolerant topology control algorithm for minimum energy consumption in these networks. More precisely, we present algorithms which preserve the connectivity of a network upon failing of, at most, k nodes (k is constant) and simultaneously minimize the transmission power at each node to some extent. In addition, we present simulations to support the effectiveness of our algorithm. We also demonstrate some optimizations to further minimize the power at each node. Finally, we show how our algorithms can be extended to 3-dimensions.

A Fast Vision System for Middle Size Robots in RoboCup

Abstract: A mobile robot should be able to analyze what it is seeing in real time rate and decide accordingly. Fast and reliable analysis of image data is one of the key points in soccer robot performance. In this paper we suggest a very fast method for object finding which uses the concept of perspective view. In our method, we introduce a set of jump points in perspective on which we search for objects. An object is estimated by a rectangle surrounding it. A vector based calculation is introduced to find the distance and angle of a robot from objects in the field. In addition we present a new color model which takes its components from different color models. The proposed method can detect all objects in each frame and their distance and angle in one scan on the jump points in that frame. This process takes about 1/50 of a second. Our vision system uses a commercially available frame grabber and is implemented only in software. It has shown a very good performance in RoboCup competitions.

Robocup-2001: the fifth robotic soccer world championships

Abstract: RoboCup-2001 was the Fifth International RoboCup Competition and Conference. It was held for the first time in the United States, following RoboCup-2000 in Melbourne, Australia; RoboCup-99 in Stockholm; RoboCup-98 in Paris; and RoboCup-97 in Osaka. This article discusses in detail each one of the events at RoboCup-2001, focusing on the competition leagues.

Basic Requirements for a Teamwork in Middle Size RoboCup

Abstract: In this paper we describe some mechanical, hardware and software aspects of our robots specially used in teamwork. The pneumatic design of the gripers and kicker enables the robot to make a good control of ball when dribbling and also passing the ball in short and long distances. The teamwork software enables our robots to perform a cooperative behavior by dividing the field to three major regions and assigning each robot a role such as defender, forward and middle in these three regions. The server can order the robots to change their role when needed and make them return to their original state after a short time.

Length-constrained path-matchings in graphs

Abstract: The path-matching problem is to find a set of vertex- or edge-disjoint paths with length constraints in a given graph with a given set of endpoints. This problem has several applications in broadcasting and multicasting in computer networks. In this paper, we study the algorithmic complexity of different cases of this problem. In each case, we either provide a polynomial-time algorithm or prove that the problem is NP-complete. © 2002 Wiley Periodicals, Inc.