Convergecast with Unbounded Number of Channels

We consider a problem of minimum length scheduling for the conflict-free aggregation convergecast in wireless networks in a case when each element of a network uses its own frequency channel. This problem is equivalent to the well-known NP-hard problem of telephone broadcasting since only the conflicts between the children of the same parent are taken into account. We propose a new integer programming formulation and compare it with the known one by running the CPLEX software package. Based on the results of a numerical experiment, we concluded that our formulation is more preferable in practice to solve the considered problem by CPLEX than the known one. We also propose a novel heuristic algorithm, which is based on a genetic algorithm and a local search metaheuristic. The simulation results demonstrate the high quality of the proposed algorithm compared to the best known approaches

Energy-efficient Area Coverage by Sensors with Adjustable Ranges

In wireless sensor networks, density control is an important technique for prolonging a network’s lifetime. To reduce the overall energy consumption, it is desirable to minimize the overlapping sensing area of the sensor nodes. In this paper, we study the problem of energy-efficient area coverage by the regular placement of sensors with adjustable sensing and communication ranges. We suggest a more accurate method to estimate efficiency than those currently used for coverage by sensors with adjustable ranges, and propose new density control models that considerably improve coverage using sensors with two sensing ranges. Calculations and extensive simulation show that the new models outperform existing ones in terms of various performance metrics

Polynomial Algorithm for Bandwidth-Delay-Constrained Multicast Routing Problem

Most network-based multimedia applications require multicasting with constraints such as bandwidth and delay in order to support group communication and their quality of services (QoS). This can be considered as the problem of constructing a multicast tree with delay and bandwidth constraints over a given network topology. This paper proposes a novel algorithm to solve this problem with a small polynomial time complexity. The algorithm covers not only the problem with uniform bandwidth and delay constraints, but also that with multiple constraints corresponding to heterogeneous groups in a service. The latter is known as an NP-Complete problem. Finally, we present simulation results over random graphs that show small connection failures. 1 Introduction Multicasting plays an important role in providing network-based multimedia services like audio and video conferencing and has been studied for many years. The study of multicasting has been mainly focused on a low-cost tree over a given..

A Deep-Submicron Steiner Tree

. A-Tree is a rectilinear Steiner tree in which every sink is connected to a driver by a shortest length path, while simultaneously minimizing total wire length. This paper presents a polynomial approximation algorithm for the generalized version of A-Tree problem with upper-bounded delays along each path from the driver to the sinks and with restrictions on the number of Steiner nodes. We refer to it as "Deep-submicron Steiner tree" as minimizing the number of Steiner nodes is crucial for signal integrity issues in deep-submicron very-large-scaled-integrated-circuit (VLSI) designs. The idea behind the algorithm is to control two parameters in order to construct a feasible (with respect to the paths delays and the number of Steiner nodes) tree of small cost. The simulation results show the high efficiency of our approach. 1 Introduction With the scaling of device technology to deep submicron dimension, gate delay is getting faster by device scaling factor S and scaled wires increase d..