Rico Radeke

Performance Study of Reconfiguration Algorithms in Cluster-Tree Topologies for Wireless Sensor Networks

This paper presents a performance study of two new proposed strategies for the reorganization of a cluster-tree and its address space: proactive and reactive algorithms. The goal of the proactive reconfiguration is to minimize the average number of hops between the possible source and destination pairs. It is achieved by attempting to reconnect nodes to a parent node with the highest possible level. The goal of the reactive reconfiguration is to reorganize the cluster on- demand when a node wishing to join the cluster cannot do it, because the possible parents exhausted their free address space. Our simulation results show that with an optimized reconfiguration a higher performance in terms of connection time and connectivity of the cluster-tree can be achieved.

Network migration using ant colony optimization

This paper describes the basic concepts of the network migration problem, as well as its cost optimal solution with an ant colony algorithm. Generally there are many possible approaches to calculate network migration strategies. One of those is to consider the migration as a Shortest Path Problem, which can be solved using meta heuristics. In this paper it will be analyzed how ant colony optimization can be used to calculate migration sequences with minimized costs. Results of our investigation are information about the speed of convergence of ant colony algorithms towards an optimal cost value. The used resource utilization to cover increasing network demands will be presented also.

On reconfiguration in case of node mobility in clustered wireless sensor networks

Wireless sensor networks are expected to be one of the key enabling technologies in the next 10 years. Protocols for such networks should be highly flexible in order to adapt to topology changes due to node mobility. In this article we focus on strategies for management of node mobility in clustered wireless sensor networks based on IEEE 802.15.4/ZigBee standards. Taking into account that modification of the cluster structure leads to performance degradation of the network reconfiguration strategies, help in avoiding long reconnection times or missing connections is required. In our work we propose a combination of proactive and reactive reconfiguration strategies to reorganize clustered structures with node mobility, leading to increased connectivity, faster reconnection times after connection loss, and building energy-efficient compact cluster-tree topologies.

CSMA/CA: Improvements of the contention window adaptation

We study the Narrowband Power Line Communications (NB-PLC) system intended to be used for Smart Grid applications. The performance of such system highly depends on the implementation and the used techniques. In this paper the Medium Access Control (MAC) layer of a specific system with the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) mechanism is studied. The main feature of the used technique is that it automatically adopts the parameters of the protocol to the dynamically changing network. We investigate the protocol and suggest the improvements that give a higher performance.

Node Degree based Improved Hop Count Weighted Centroid Localization Algorithm

Hop-count based weighted centroid localization is a simple and straightforward localization algorithm, which uses anchors with known positions and the hop count to these anchors to estimate the real position of nodes. Especially in sensor networks, where energy restrictions prevent more complex algorithms, this fast and simple algorithm can be used. Unfortunately the localization error of the algorithm can hinder the practical usage. In this paper we will improve the weighted centroid algorithm for hop count based localization by adding the node degree on the paths to the referenced anchors into the weights. After an analysis to obtain theoretically optimal coefficients we will show by means of simulation that for longer hop counts to the anchors and areas with different node degrees the proposed ND-WCL algorithm outperforms the known hop count based weighted centroid localization algorithm.

Optimization of energy efficient network migration using harmony search

In this paper we describe the basic network migration problem in backbone networks to move from an existing to a new technology. Furthermore we use a generic harmony search algorithm to optimize the solution in terms of energy efficiency and costs. Harmony search is a probabilistic meta-heuristic which has been successfully adapted to many optimization problems. We analyze how harmony search can be used to calculate migration sequences with minimized energy consumption and financial costs. Results of parameter studies for the heuristic will be shown to evaluate the method. The achieved resource utilization to cover increasing network demands and the point of introduction within a certain time interval will be presented also.

Network Migration Optimization Using Genetic Algorithms

This paper introduces the problem of communication network migration for backbone networks. Heuristic solutions for this problem can be determined by the application of genetic algorithms to the problem. A description of the system model is presented, as well as the used algorithmic approaches and optimization results. Our main goal is the optimization of migration costs, by respecting increasing demands over the migration period, while device costs per bit are decreasing. We will present Crowded DPGA as best found GA to solve the network migration problem.

Enhancement of backoff algorithm in CSMA/CA protocols for broadband PLC

Improvement of communication protocols for energy management purposes has become a challenging part of smart grid systems development. Powerline communications (PLC) has many advantages for being used in this area. Many PLC communication protocols use CSMA/CA channel access schemes on Multiple Access Protocol (MAC) layer. This paper presents an enhancement of the CSMA/CA broadband PLC protocols operation by application of special method for backoff generation. The proposed improvement is applicable to different CSMA/CA protocols. The resulting CSMA/CA schemes maintain interoperability with the original ones. The performance of the improved algorithm is shown by means of a mathematical model and by simulation.

Improving network migration optimization utilizing memetic algorithms

In this paper we describe the basics of the network migration problem, as well as the solution of the problem using meta heuristics. The class of heuristics described and applied in this paper is called memetic algorithms. Those are explained and results regarding network migration are presented. To evaluate potential algorithm candidates a generic TSP has been implemented and tested. The mapping of the network migration problem to memetic algorithms and to the algorithm library GALib is explained as well. Our main goal is the optimization of network migration costs, by respecting increasing demands over the migration period, while device costs per bit are decreasing. The mapping of the specified problem to the heuristic variants is also of major interest.

QoS concept for IEEE 802.16-2012 based WiMAX networks

Worldwide Interoperability for Microwave Access (WiMAX) mobile communication systems deliver all services through the Internet Protocol. Therefore, an important and crucial part of such systems is the Quality of Service (QoS) support to fulfill the needs of real-time applications. The underlying IEEE 802.16 standard specifies the QoS entities and signaling, but all algorithms are left open for vendor differentiation. In this paper, we propose a Mobile WiMAX QoS concept. It consists of a QoS aware traffic shaping and scheduling algorithm. In contrast to other proposals, our scheduling algorithm does not differentiate between service classes, but between the guaranteed and sustained traffic rate specified by the IEEE 802.16-2012 standard. Our Two-Rate-Based Scheduler (TRBS) additionally accomplishes fairness based on radio resources between users after fulfilling guaranteed demands. Large scale simulation results show that our TRBS algorithm satisfies the QoS requirements of real-time flows. The comparison to Proportional Fair scheduling by means of the number of supported VoIP users and system goodput reveals a significantly better system performance of our scheduling algorithm in highly loaded cells.