Telfor Journal Vol.2 No.2 (2010)

Content

Editorial HyperLink
Editor-in-Chief: Prof. Dr Đorđe Paunović

Improving OFDM/DQPSK System Performance in the Conditions of Frequency Offset Existence

Z.B. Nikolić, B.R. Dimitrijević, N.D. Milošević, and S.N. Stošović
Topic:
Communication Theory
Abstract
The basic characteristics of Orthogonal Frequency Division Multiplex (OFDM) systems with DQPSK modulation and channel estimation with an adaptive transversal filter and LMS algorithm are analyzed and presented in this paper. In the simulation environment designed for this purpose, we analyzed the effects of frequency offset on the performance of OFDM digital communications and presented the method for improving system performance in the presence of frequency offset. We analyzed the influence of OFDM system parameters on system’s performance for various values of frequency offsets, filter lengths and the number of subcarriers. Finally, we compared the result with the one for a perfectly synchronized OFDM/DQPSK system with differential and coherent demodulation.
Keywords
orthogonal frequency-division multiplexing, differential quadrature phase-shift keying, frequency offset, frequency synchronization, LMS algorithm, adaptive transversal filter.
Full Text
HyperLink Improving OFDM/DQPSK System Performance in the Conditions of Frequency Offset Existence
Page(s)
64-67

Design and Implementation of Adaptive Turbo Encoder for Quantized Software Defined Low-Power DVB-RCS Radios

S.W. Shaker and S.H. Elramly
Topic:
Communication Theory
Abstract
Turbo codes are employed in every robust wireless digital communications system. Those codes have been adopted for the satellite return channel in DVB-RCS (Return Channel via Satellite) standard. In Software Defined Radios (SDRs), Field Programmable Gate Array technology (FPGA) is considered a highly configurable option for implementing many sophisticated signal processing tasks. The implementation for such codes is complex and dissipates a large amount of power. This paper studies the efficient implementation of quantized DVB-RCS turbo coding. Also, a low-power, turbo encoder for DVB-RCS is described using a VHDL code. The proposed encoder design is implemented on Xilinx Virtex-II Pro, XC2vpx30 FPGA chip. FPGA Advantage Pro package provided by Mentor Graphics is used for VHDL description and ISE 10.1 by Xilinx is used for synthetization.
Keywords
DVB, FPGA, Quantization, Software Defined Radios, Turbo codes, VHDL.
Full Text
HyperLink Design and Implementation of Adaptive Turbo Encoder for Quantized Software Defined Low-Power DVB-RCS Radios
Page(s)
68-73

Determination of Morphologically Characteristic PCG Segments from Spectrogram Image

A.M. Gavrovska, M.P. Paskaš, and I.S. Reljin
Topic:
Signal Processing
Abstract
The three-dimensional presentation of phonocardiac signal, simultaneously considering time, amplitude and frequency, allows the determination of morphological characteristic segments in phonocardiogram (PCG), both in short and long sequences. For this purpose, the STFT (Short-Time Fourier Transform) spectrogram images were used. By applying some methods known from image processing it is possible to recognize and extract basic heart sounds and murmurs from such time-frequency images. The method is tested over several characteristic test phonocardiac signals.
Keywords
Morphological processing, murmur, phonocardiogram, spectrogram, STFT.
Full Text
HyperLink Determination of Morphologically Characteristic PCG Segments from Spectrogram Image
Page(s)
74-77

Adaptive Channel Estimation based on Soft Information Processing in Broadband Spatial Multiplexing Receivers

P. Beinschob and U. Zölzer
Topic:
Signal Processing
Abstract
In this paper we present a novel approach in Multiple-Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) channel estimation technique based on a Decision Directed Recursive Least Squares (RLS) algorithm in which no pilot symbols need to be integrated in the data after a short initial preamble. The novelty and key concept of the proposed technique is the block-wise causal and anti-causal RLS processing that yields two independent processings of RLS along with the associated decisions. Due to the usage of low density parity check (LDPC) channel code, the receiver operates with soft information, which enables us to introduce a new modification of the Turbo principle as well as a simple information combining approach based on approximated aposteriori log-likelihood ratios (LLRs). Although the computational complexity is increased by both of our approaches, the latter is relatively less complex than the former. Simulation results show that these implementations outperform the simple RLS-DDCE algorithm and yield lower bit error rates (BER) and more accurate channel estimates.
Keywords
MIMO, OFDM, Channel Estimation, Turbo Receiver Processing, LDPC Codes.
Full Text
HyperLink Adaptive Channel Estimation based on Soft Information Processing in Broadband Spatial Multiplexing Receivers
Page(s)
78-81

Analysis of just Noticeable Difference in Spectrum of Church Bell Sound

A. Samolov
Topic:
Multimedia
Abstract
Bells are specific sound sources. They have distinct, but, unlike musical instruments, inharmonious partials. These partials arise from modes of vibration of the bell and depend on dimensions and potential irregularities of the bell. Therefore, the question of a just noticeable difference in the church bell sound is of great importance. Analysis of subjective tests with synthetic sounds of two bells, different in size, is described in this paper. We report results for a just noticeable difference of partial frequency in the range 10-15 cents. Frequency dependence, is also, noticed.
Keywords
church bell, just noticeable difference, subjective test.
Full Text
HyperLink Analysis of just Noticeable Difference in Spectrum of Church Bell Sound
Page(s)
82-85

Reverberation Radius in Real Rooms

M. Mijić and D. Mašović
Topic:
Multimedia
Abstract
A reverberation radius, also called a critical distance, is an important parameter in sound reproduction. Statistical approach gives a simple formula for its calculation, and some simple methods for its measurement were described in literature. To measure the critical distance in real rooms, a more accurate method is proposed. This paper is concerned with that method. Accuracy of the method was analysed and the results of critical distance measurement in several rooms of different sizes and acoustical characteristics are presented.
Keywords
critical distance, reverberation radius, room acoustics, sound reproduction.
Full Text
HyperLink Reverberation Radius in Real Rooms
Page(s)
86-91

Influence of Diffusivity in Room on its Acoustic Response

Dragana Šumarac Pavlović and Milan Petrović
Topic:
Multimedia
Abstract
Diffusivity is a geometrical feature of the room which is proportional to the dimension of relief on its interior surfaces. This paper presents the results of analysis which investigates the correlation between diffusivity in a room and parameters calculated from a recorded impulse response. The analysis was performed using a specially prepared physical model of a parallelepipedic room with different combinations of flat and diffusive interior surfaces.
Keywords
absorption, acoustic measurement, diffusion, impulse response, physical model.
Full Text
HyperLink Influence of Diffusivity in Room on its Acoustic Response
Page(s)
92-97

Efficient Modeling of Complex Electromagnetic Structures Based on the Novel Algorithm for Spatial Segmentation Using Hexahedral Finite Elements

S.V. Savić, M.M. Ilić, B.M. Kolundžija, B.M. Notaroš
Topic:
Applied Electromagnetics
Abstract
A new algorithm for spatial segmentation using hexahedral finite elements, combined with the algorithm for spatial segmentation using quadrilateral elements, is presented. Problems with combining the algorithms for segmentation by hexahedral and quadrilateral elements in the hybrid FEM-MOM technique are pointed out. An example of analysis of a scatterer at resonant frequency is given.
Keywords
Electromagnetic analysis, finite element methods, geometrical modeling, hybrid techniques, meshing, method of moments.
Full Text
HyperLink Efficient Modeling of Complex Electromagnetic Structures Based on the Novel Algorithm for Spatial Segmentation Using Hexahedral Finite Elements
Page(s)
98-101

Intelligent Servo Drives Control Based on a Single Fieldbus Network

D. Puiu and F. Moldoveanu
Topic:
Applied Electronics
Abstract
Due to the quick evolution of manufacturing processes, the demand for more flexible automation systems is on the rise. To answer these requirements, distributed motion control architecture based on intelligent drives tends more and more to replace the traditional solutions. This paper presents the control of an articulated arm robot with two local intelligent servo drives connected on a CAN network to a motion controller which receives the trajectory of the robot from a computer. The control structure is based on a single CAN network where local intelligent servo drives, a motion controller and a computer are connected.
Keywords
articulated arm robot, CAN network, intelligent servo drives, distributed control system, motion coordinator.
Full Text
HyperLink Intelligent Servo Drives Control Based on a Single Fieldbus Network
Page(s)
102-106

Home Appliances as Home Controllers: Concepts and Set-Top Box Implementation

M.Z. Bjelica, N. Teslic, Z. Jovanovic, and Z. Marceta
Topic:
Applied Electronics
Abstract
In this paper we present a novel softwarebased home control platform suitable as an extension to digital home appliances that are equipped with a CPU (settop boxes, home theatre systems, TV sets, gaming consoles, etc). By using an appliance they are already accustomed to, users become able to control lights, appliances and media playback in their homes. Intelligence and awareness are achieved with a support for execution of recipes – preprepared scripts that define timely actions and respond to triggers obtained from sensors. Software abstraction layer facilitates integration of any desired communication protocol. In our prototype, we supported Zigbee and DMX for light control, X10 for light/appliances control over power line, as well as Ethernet-based optical cameras as motion/presence sensors and UPnP/DLNA based equipment for distributed media playback.
Keywords
domotics, smart home, set-top box, Zigbee, DMX, home automation.
Full Text
HyperLink Home Appliances as Home Controllers: Concepts and Set-Top Box Implementation
Page(s)
107-112