Issue editor: Paweł Szulakiewicz
The second issue of Advances in Electronics and Telecommunications contains sixteen selected papers presented at the last two editions of Poznań Telecommunications Workshop: PWT 2007 and 2008 (www.pwt.et.put.poznan.pl). The conference held annually in Poznań at the beginning of December is devoted to topics concerning research and education in telecommunications, electronics, and related fields. These most important areas of Information and Communication Technologies focus the attention of the workshop participants, who are mainly young researchers and PhD students from Polish universities of technology.
The PWT workshops in Poznań have become a forum for developing a wide range of professional relationships. Both the presentations of research results and the discussions that follow provide the young authors with valuable opportunities to interact with more experienced scientists, industry professionals and innovators in the fields of their particular interests.
Jerzy Kasperek, Andrzej Nikoniuk, Paweł J. Rajda
This paper provides information on the construction and presents experience from the “Koliber” project: a modern multipurpose radio system for railways. The radio equipment is produced by Radionika sp. z o.o., and was designed in cooperation with Department of Electronics, AGH University of Science and Technology. Discussed here are system architecture, technical and functional parameters, and innovative radio system applications possible thanks to its innovatory construction.
Dariusz Kościelnik, Jacek Stępień
This article presents description of the simulation study of the low rate wireless personal area networks, defined by the IEEE 802.15.4 standard. The obtained results make available an evaluation of the effective transmission rate of a transmission channel, the resistance to the phenomenon of hidden station as well as sensibility to the
problem of the exposed node.
This paper is to analyze an improvement in performance of WLAN (Wireless Local Area Network) systems introduced by space and space-time diversity, as well as spatial multiplexing. These MIMO (Multiple-Input Multiple-Output) techniques are approved in the latest 802.11n specification. In order to perform the experiment, a Matlab application, that simulates WLAN physical layer, has been developed.
In this paper the asymptotic performance of a new intuitive space-time diversity scheme is analyzed. So called boosted scheme is compatible with today’s WLAN specifications with regard to convolutional coding and bit labelling, and minimizes the number of decoding iterations, required to obtain a reasonable Bit Error Rate. Good properties of the proposed scheme are proved by high asymptotic coding gain and advantageous distance spectrum. Simulation experiment is to investigate the system performance in terms of poor channel state. The boosted scheme is compared with its ancestor – Bit-Interleaved Space-Time Coded Modulation with Iterative Decoding (BI-STCM-ID).
Rafał Zdunek, Maciej J. Nawrocki
Krylov subspace methods, which include, e.g. CG, CGS, Bi-CG, QMR or GMRES, are commonly applied as linear solvers for sparse large-scale linear least squares problems. In the paper, we discuss the usefulness of such methods to optimization of WCDMA networks. We compare the selected methods with respect to their convergence properties and computational complexity, using a typical uplink model for a WCDMA network. The comparison shows that the GMRES method is the most suitable for our task.
Agnieszka Chodorek, Robert Chodorek
The TCP-Friendly Rate Control (TFRC) protocol manifests strong equality towards competing TCP or TCP-friendly flows. Although the RFC 3448 suggest, that TFRC is suitable for multimedia, this equality is a great disadvantage in the case of transmission of multimedia over the TFRC.
The TFRC emulates TCP-like congestion control using the TCP throughput equation. In the paper, we substitute TCP throughput equation recommended for the TFRC by linear throughput equation. Simulation results show, that proposed solution is more suitable for multimedia than the equation proposed in RFC 3448. Experiments were carried out using an event-driven ns-2 simulator, developed in U. C. Berkeley.
Michal Czarkowski, Sylwester Kaczmarek
Current packet networks use a large variety of mechanisms which should support QoS (Quality of Service). One of those mechanisms is routing (calculating connection paths for incoming service requests). The most effective in QoS context is dynamic routing which is based on the current network state described by offered traffic matrix and link states. Connection paths changes after switching between calculated available paths may cause that received packets have changed order within a single stream. Following paper includes problem definition and analysis of all additional effects. Combined model simulation/analytic has been pro-posed which shall find the answer if the number of changed packets order is significant and if it should be considered when calculating the end-to-end delay balance in analytical models for packet networks with differentiated services. Pro-posed model gave also the answer how often calculated paths may be switched to avoid network to be out of tune.
In this paper new packet dispatching schemes for efficient support of the uniform as well as the nonuniform traffic distribution patterns in Memory-Space-Memory (MSM) Clos-network switches are presented. Three such schemes, called Static Dispatching-First Choice (SD-FC), Static Dispatching-Optimal Choice (SD-OC) and Input Module (IM)-Output Module (OM) Matching (IOM), are proposed and evaluated. The algorithms are able to unload the overloaded input buffers employing a central arbiter. This effect is a desirable feature especially for effective support of
the nonuniform traffic distribution patterns. We show via simulation that the proposed schemes deliver very good performance in terms of throughput, cell delay and input buffers size under different traffic distribution patterns. The results obtained for proposed algorithms are compared with results obtained for selected request-grant-accept iterative packet dispatching schemes.
Andrzej Dobrogowski, Michał Kasznia
In this paper the methods enabling real-time calculation of two commonly used parameters of timing signals – Allan deviation (ADEV) and time deviation – are presented. The idea of real-time computation of both parameters is described. The results of experimental tests of the methods enabling separate as well as joint real-time ADEV and TDEV computation are presented and discussed.
Krzysztof Lange, Michał Kasznia
The paper discusses potential applications of the time vernier principle, based on the so-called Vernier interpolation. It presents the application of this method to precise time interval measurement and to the results of construction work.
A new method of improving properties of number sequences produced by a multiplicative congruential pseudorandom generator (MCPG) was proposed. The characteristic feature of the method is the simultaneous usage of numbers generated by the sawtooth chaotic map, realized in a finite-state machine, and symbols produced by the same map. The period of generated sequences can be significantly longer than the period of sequences produced by a multiplicative congruential pseudorandom generator realized in the same machine. It is shown that sequences obtained with the use of the proposed method pass all statistical tests from the standard NIST statistical test suite v.1.8.
Piotr Remlein, Dawid Szłapka
In this paper a method of using convolutional codes over rings for packet data transmission over additive white gaussian noise (AWGN) channel is proposed. The tailbiting method is generalized and applied to convolutional codes based on ring of integers modulo-M. The codes were named as tailbiting codes over ring (TBR). This paper presents a method to desing TBR codes obtained by a concatenation of feedback convolutional encoder over ring and M-QAM modulator. In the paper it is described how a systematic ring convolutional encoder with feedback can obtain the same starting and ending state. The best TBR codes with different number of encoder states for 16-QAM modulated symbol sequences of varying lengths are tabulated.
Step index fiber modeling process is carried out through numerically solving of eigenvalue equation to calculate propagation constant for fundamental mod. Input data in the process is only index of refraction calculated from Sellmeier dispersive formula for appropriate mol percentage doping of germanium dioxide in silica glass fiber. Output data in the modeling process is optimal value of the normalized frequency, which guarantees that single mode operation region is equal to bright soliton propagation region. Final verification of the process is soliton generation up to sixthorder inside such modeled fiber. In this end nonlinear Schödinger equation is solved numerically for initial condition of hyperbolic secant form. Maximization of single mode operation and bright soliton propagation region is essential in wavelength division multiplexing technique.
In the paper the impact of carrier transport effects on the chirp modelling of quantumwell lasers is investigated. Particularly, the difference between the full modelling based on quantum-well laser rate equations is compared with modelling based on formulas derived for bulk lasers. As it was shown the relations between chirp and intensity modulation are quite similar in booth cases.
Przemysław Krehlik, Łukasz Śliwczyński, Grzegorz Sikorski
In the paper the idea and practical realization of a measurement system dedicated for highly attenuated eye diagrams diagnostics is presented . It is specially oriented on of highspeed modulated optical data transmission signals, which amplification is difficult and/or undesired. Presented measurements displayed usefulness of proposed solution.
Łukasz Śliwczyński, Przemysław Krehlik
In the paper, the bit error rate tester suitable for operation in 10 Gb/s fibre optic links is described. The BER tester was built from commercially available components. Generation and reception of 10 Gb/s data stream is performed with help of high-speed serialiser and deserialiser by Maxim. The main functions of the BER tester are implemented in the field programmable gate array (FPGA) Spartan3 device by Xilinx. The part of the FPGA runs with the clock speed equal to 622 MHz. Some measurement results obtained in the fibre optic links operated with 10 Gb/ data rate are also presented.