ETF Journal of Electrical Engineering

8

Authors: Uglješa Urošević, Zoran Veljović

In this paper, MIMO OFDM-CDMA downlink scheme is proposed as a solution for performance improvement of the OFDM-CDMA downlink system with pilot tone and threshold detection combining (optimum TDC). The new presented system with MIMO included uses space-time block coding applied to two, three and four transmit antennas. BER (Bit Error Rate) performance in the case of Ricean frequency selective fading is evaluated for the original system as well as for the one with MIMO included. For that reason an adequate simulation model is developed. The results show that for the same data rate the proposed system with two times less subcarriers, i.e. narrower occupied frequency band provides better BER performance than the OFDM-CDMA system with pilot tone.

10

Authors: Nataša Savić, Zoran Milivojević, Darko Brodić

In the first part of this paper the parametric quadratic convolution kernels were presented, i.e. Dodgson kernel and the proposed kernel. The analytical expressions for the position of the maximum interpolation function were determined. The second part of this paper represents the results of application of the convolution interpolation with the described parametric kernels in estimation of the frequency of the signal in the spectral domain. In addition to that the efficiency of the estimation of the frequency of the signal in case when AWGN was superimposed to the signal if SNR=0-50dB was analyzed. As a measure of successfulness of estimation the mean square error was used. The analysis of the results shown both graphically and tabular determined the optimal value of the kernel parameter and the corresponding window function.

10

Authors: Luka Filipović, Božo Krstajić

This paper presents modified master-slave algorithm for load balancing improvements in parallel applications. The proposed algorithm combines static and dynamic algorithms and improves load balancing during critical parts of task execution. Use of the proposed algorithm causes a reduction in execution time of parallel application and increase of utilization of parallel computer resources. Simulation results using the proposed modified master-slave algorithm approved reduction in execution time and better occupancy of parallel infrastructure.

10

Authors: Slavica Tomović, Milutin Radonjić, Igor Radusinović

Quagga is an open-source software platform that provides routing services. It supports the following IP routing protocols: RIPv1, RIPv2, RIPng, OSPFv2, OSPFv3, IS-IS, BGP4 and BGP4+. Quagga is unique in its design because it uses a separate process for each running protocol. This platform offers true modularity since each protocol module can be upgraded or configured independently of the others. In order to illustrate its capabilities, this paper investigates support of this platform for RIP and OSPF, two most commonly used routing protocols on the Internet. In addition, the results of convergence time measurements are presented. Considering that software defined networking (SDN) promise to be Future Internet platform, brief description of possible application scenario for Quagga in SDN networks is provided.

11

Authors: Milica Medenica, Sanja Zuković, Andjela Draganić, Irena Orović, Srdjan Stanković

This paper describes comparison of algorithms for Compressive Sensing reconstruction of 2D signals. Compressive Sensing is a new signal sensing approach aiming to decrease the requirements for resources in real digital systems (number of sensors, memory requirements, etc.). This method provides signal analysis and reconstruction using small set of randomly chosen samples. Reconstruction is based on complex mathematical algorithms - optimization algorithms. Depending on the signal type, different optimization algorithms are used. This paper deals with three algorithms for CS image reconstruction. Performances of the algorithms are compared for different types of 2D signals. Reconstruction quality is measured by calculating PSNR between original and reconstructed signal. Execution time for each considered algorithm is calculated, as well.

11

Authors: Veljko Milutinović

This paper focuses on designing and programming a DataFlow computer by modifying existing algorithms for better hardware utilization. Maxeler Technologies provides libraries for transforming Java-like time-critical code into the FPGA configuration files in compile-time, while C, C++, or FORTRAN code executes on the CPU and makes function-calls to start the calculation on the hardware. Using the tools from the manufacturer of the underlying FPGA technology, a .max file is formed and linked with the compiled .c code and the appropriate runtime routines, forming the executable for the control flow host. Since compilation is performed down to levels much below the machine code level (to register transfer level, gate transfer level, and transistor transfer level), the DataFlow paradigm offers better utilization of the chip for the program it is built for, making execution faster and power dissipation lower. The proposed technology is best used if the BigData can be partitioned into chunks of appropriate sizes. The time of DataFlow architecture is yet to come, mostly due to the facts that the FPGA technology and the compiler technology continue to improve; therefore, the amount of applications of DataFlow technology will increase drastically.

14

Authors: Novica Daković, Milovan Radulović

This paper presents simulation of the motion of autonomous vehicle using the flatness based control. Based on the kinematic model of the vehicle motion a feed-forward trajectory tracking controller has been designed. For the system stabilization in the presence of disturbances a feedback controller based on linear error dynamics has been constructed. In either case, comparative study between real moving and desired one has been presented.