Jan Prokopec

Fundamental oscillators based on diamond transistors

This paper brings complete list of the simplest network structures capable to generate harmonic signals. The core elements used are modern analog building blocks known as the diamond transistors. Utilized design procedure is based on the prescribed state space representation of the second-order oscillators such that the final circuits contain minimum amount of the components and its basic frequency can be electronically adjusted. Each oscillator has been analyzed numerically, verified by the Pspice simulations as well as validated experimentally. The selected results of some importance are included. Since the nonlinear higher-order complex motions have been recognized during the measurement this behavior is briefly discussed.

Propagation path loss models for mobile communication

Signal propagation and path losses are the key elements of wireless network design. This paper describes tuning process of empirical propagation path loss models for typical environments (urban, suburban, open areas). The Hata based models were compared with data measured in Brno. Model corrections were suggested and tested for GSM frequency band. The correction is aimed on the short range propagation in cellular networks. For model fitting to the measured data and for a deviation error estimation was used the mean square error (MSE). The tuned propagation model was used for localization in cellular network using particle swarm optimization (PSO) technique and geometrical technique.

Influence of mobile network interfering products on DVB-T/H broadcasting services

In this paper the influence of mobile network interfering products on DTV (Digital Television) services is explored and evaluated. More precisely, the overall aim of this paper is to measure and show the interactions between the mobile (GSM) and digital terrestrial television (DVB-T/H) broadcasting networks and services. In the DVB-T/H system configuration, the TPS (Transmission Parameter Signaling) carriers keep the receiver informed about the main system parameters. Disturbance of these carriers by interfering products of GSM network and degradation of DVB-T services are also explored and described. Theoretical backgrounds, general workplace and the principle of the measuring method is also introduced and briefly described. For the evaluation of the impact of mobile networks on the signal quality of DTV services the BER (Bit Error Ratio), MER (Modulation Error Ratio) ratios and constellation imperfections are used. Finally, the obtained results are evaluated and clearly described.

Exploring and measuring the co-existence between LTE and DVB-T2-Lite services

The development and effective use of wireless communication systems to provide mobile services is rapidly increasing. Nowadays, the worlds most perspective standards to provide wireless multimedia services in high quality are LTE (Long-Term Evolution) and DVB-T2 Lite (DVB-2nd Generation Terrestrial). On the other hand, these wireless multimedia systems can many times operate in a neighboring frequency spectrum. Therefore, as a result, numerous co-existence scenarios are possible. The focus of this paper is to explore and measure the co-existence between LTE and DVB-T2 Lite multimedia services. Theoretical backgrounds of the coexistence scenarios, general workplace and the principle of the measuring method of the influence of the LTE services on DVB-T2 services and vice versa are clearly presented and described. Furthermore, deeper investigation of the mutual influence of the DVB-T2 system on the LTE system is also explored and graphically illustrated. Finally, all obtained results are evaluated and future work is outlined.

Some practical experiments with simple driven dynamical systems

A subclass of the second-order driven chaotic systems have been verified and this brief paper brings some results. In this work a harmonic signal is supposed to be a driving force. By considering its frequency to be the natural bifurcation parameter the associated spectrum of the Lyapunov exponents are repeatedly calculated by using Mathcad. The generated signals in the time domain are presented as the selected oscilloscope screenshots as well as the associated plane projections.

DVB-H Standard and Testing of its Mobile Terminals

This paper deals with the characteristics of the DVB-H standard features and transmission of digital television to the DVB-H mobile terminals. The methodology of the mobile terminals testing is introduced including the specific transmission system in the laboratory of digital television and mobile communications DREL BUT. This can be used for efficient analysis in research and development of DVB-H broadcasting and its terminals.

Two Dimensional Signal Spreading in UMTS LTE: Exploiting Time-Frequency Diversity to Increase Throughput

This paper proposes a two-dimensional spreading method in UMTS Long Term Evolution (LTE). Such a method brings additional time-frequency diversity which is beneficial in terms of the ability to decode transmitted data at the receiver site under multipath fading. Additional diversity is provided due to the fact that chips of transmitted signals are spread using a Walsh-Hadamard spreading sequence over several subcarriers as well as over several time-slots simultaneously. A comparison with state-of-the-art LTE downlink transmission is provided. To enable reproducibility and to increase credibility of our results, an open source Vienna LTE simulator is utilized. LTE transmissions with the proposed 2D spreading are tested on several channel models. Simulations show that apart from an Additive White Gaussian Noise channel model, this 2D spreading based method outperforms the throughput performance of standard LTE. At high Signal to Noise Ratio (SNR), the throughput increase in most channel models is higher than 10 %.

Efficiency of encoding schemes in mobile WiMAX

Mobile WiMAX (Worldwide Interoperability for Microwave Access) standardized by IEEE 802.16e is a broadband wireless system based on Scalable OFDMA (Orthogonal Frequency Division Multiple Access). This standard is suitable for the last mile connection in areas where it is not possible to build wired infrastructure, nevertheless it provides a broadband connection for nomadic users and supports cellular structure. Its main advantage compared to Wi-Fi standard is the possibility of a very powerful handling of radio resources allocation to users in order to adjust quality of radio-environment and number of active users at given area. This article investigates impact of different encoding schemes used in Mobile WiMAX to theoretical throughput and deals with efficiency evaluation of these schemes.

Indoor channel modeling based on experience with outdoor urban measurement — Multislope modeling

This paper discusses indoor channel modeling for mobile communications. We apply multislope log-distance channel model and simulate indoor path loss distribution. The standard deviation value of normal and log-normal distribution describes various fading effects affecting the signal propagation. We defined the areal signal path loss distribution in a restricted indoor environment. The PSO-based process with the MSE estimation determinates the multi break point model for the tested building. Results of our work are the optimized MSE fitted multislope models.

Wireless transmission of video signal at very low bitrate

The contribution describes a basic structure of the low rate wireless encoder and its application in domain of the video signal transmission. Also, the experimental results with real video sequences encoded by a three-dimensional discrete cosine transform coder will be presented. Finally, compress ratio and picture quality values will be published as well.