ETF Journal of Electrical Engineering

10

Authors: Milan Kočović, Zoran Miljanić, Ilija Vujošević

This paper presents the application of dynamic programming method in the hydro-thermal coordination, which is based on finding the optimal trajectory of the use of water in reservoir storage with the limitation of initial and final storage volumes. Initial and final volumes of the reservoir present the input data in the optimization and which were obtained in short-term planning of water consumption. Also, this paper presents the modeling and the possible approximations of the inputoutput characteristic of steam and hydroelectric plants. For the purpose of hydrothermal coordination, the program was implemented using MATLAB software and its graphical user GUI interface. The mentioned program includes hydro-thermal coordination that was made on the principle of dynamic programming using Dijkstra algorithm.

10

Authors: Gojko Gogić, Slavica Tomović, Igor Radusinović

In this paper, we present results of performance evaluation of OpenFlow data-center (DC) network testbed, developed as part of BIO-ICT research and innovation platform. The testbed provides rich testing environment for experimental research in the area of software-defined networking (SDN), which is widely recognized as a fundamental technology for next generation DCs. The cost-efficient and solid performance testbed design is achieved with the heterogeneous data plane, consisted of software and hardware OpenFlow switches. In order to identify the most suitable solution for the control plane, we compared performance of four open-source SDN controllers (ONOS, Floodlight, POX and Ryu) via Cbench benchmarking tool. In addition, we have conducted several testbed experiments which provide useful insight into the data plane performance when different controllers are used. The obtained results indicate that Floodlight controller outperforms ONOS, POX and Ryu controllers in terms of throughput, processing latency and scalability.

11

Authors: Jovana Mrkić, Enis Kočan

Orthogonal frequency division multiplexing (OFDM) with index modulation (IM) is a recently proposed modulation technique for performance improvement of OFDM based systems. The basic concept of this modulation scheme assumes that the information is conveyed to the receiver by standard M-ary signal constellations and, at the same time, by the indices of the active OFDM subcarriers which are chosen for carrying those constellation symbols. Due to the additional information bits transmitted in that way, spectral efficiency of the system is increased, as well as energy efficiency, because not all OFDM subcarriers are active in transmission. However, these performance improvements are achieved at the price of bit error rate (BER) degradation at lower signal-to-noise ratio (SNR) values. In this paper we examine BER performance of OFDM-IM system in case of frequency selective fading channels, assuming both Rayleigh and Rician fading statistics.