Institute of Electron Technology
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2189 research outputs found
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Interleaving Technique Implementation to Reduce PAPR of OFDM Signal in Presence of Nonlinear Amplification with Memory Effects, Journal of Telecommunications and Information Technology, 2018, nr 3
Get PDFIn OFDM systems, peak-to-average power ratio (PAPR) reduction of the signal is one of the main challenges that need to be overcome in order to use the transmitter in an efficient manner. As one of attractive techniques, interleaving can be used in PAPR reduction for multicarrier signals without spectrum distortion. In this paper, the authors propose to extend the possibilities of interleaving to improve PAPR reduction, to use a new coding of interleaver keys at the transmitter and a robust decoding procedure at the receiver. In order not to degrade the data rate, the use of null subcarriers to transmit side information to the receiver is proposed and evaluated. Simulation results in the context of the WLAN 802.11a standard in the presence of a nonlinear power amplifier model with memory, show a reduction of PAPR of approximately 5.2 dB, and an improvement of bit error rate and error vector magnitude of about 2 decades and 4% respectively, while respecting the spectral mask specification
Examples of Objectified Multiple Criteria Ranking in the Selection of Infrastructural Projects, Journal of Telecommunications and Information Technology, 2018, nr 4
Get PDFThe paper addresses the issue of multiple criteria rankings of infrastructural projects (buildings, roads, etc.). Although the amount of literature devoted to this subject is considerable, all methods proposed produce subjective rankings, dependent on a direct or indirect definition of weighting coefficients applicable to subsequent evaluation criteria. Infrastructural projects are usually selected and approved collegially, however, by a group of decision makers with preferences that may potentially differ significantly. Therefore, an objectified ranking, independent from subjectively defined weighting coefficients, is needed for infrastructural projects. Such a ranking is proposed, analyzed and applied by the authors of this paper. This ranking depends originally only on the multiple objective evaluation data, i.e. the values of evaluation criteria related to decision scenarios or alternatives. Such an approach does not render a fully objective ranking, since one of this kind does not exist at all. Even the choice of the ranking method is a subjective decision, but it is objectified to the extent possible. The paper presents several examples of multiple criteria evaluation of infrastructural projects, derived from literature, and compares subjective rankings published in literature with objectified rankings that are independent of weighting coefficients
Video Streaming over IP using the DASH Technique, Journal of Telecommunications and Information Technology, 2018, nr 2
Get PDFModern Internet serves as a high-performance platform for an ever-increasing number of services. Some of them – video services in particular – are of the broadband variety. So, it is not surprising that segments of networks can rapidly become congested, which may lead to a deterioration in quality. It is hoped that the new MPEG-DASH technique will alleviate congestion. This paper contains an analysis of the new technology’s impact on the quality of service in IP networks. It also explains a new numerical tool QoSCalc(DASH) that has been used to analyze the DASH method in different scenarios. The results are presented graphically and interpreted
Suitable Spreading Sequences for Asynchronous MC-CDMA Systems, Journal of Telecommunications and Information Technology, 2018, nr 3
Get PDFIn order to meet the demand of high data rate transmission with good quality maintained, the multi-carrier code division multiple access (MC-CDMA) technology is considered for the next generation wireless communication systems. However, their high crest factor (CF) is one of the major drawbacks of multi-carrier transmission systems. Thus, CF reduction is one of the most important research areas in MC-CDMA systems. In addition, asynchronous MC-CDMA suffers from the effect of multiple access interference (MAI), caused by all users active in the system. Degradation of the system’s bit error rate (BER) caused by MAI must be taken into consideration as well. The aim of this paper is to provide a comparative study on the enhancement of performance of an MC-CDMA system. The spreading sequences used in CDMA play an important role in CF and interference reduction. Hence, spreading sequences should be selected to simultaneously ensure low CF and low BER values. Therefore, the effect that correlation properties of sequences exert on CF values is investigated in this study. Furthermore, a numerical BER evaluation, as a function of the signal-to-noise ratio (SNR) and the number of users, is provided. The results obtained indicate that a trade-off between the two criteria is necessary to ensure good performance. It was concluded that zero correlation zone (ZCZ) sequences are the most suitable spreading sequences as far as the satisfaction of the above criteria is concerned
Pole elektromagnetyczne – źródła, regulacje i pomiary, Telekomunikacja i Techniki Informacyjne, 2018, nr 1-2
Get PDFW artykule przedstawiono podstawowe problemy związane ze środowiskiem elektromagnetycznym, naturalnymi i wytwarzanymi przez człowieka źródłami pola elektromagnetycznego (PEM). Następnie omówiono zagadnienia prawnej ochrony człowieka i środowiska przed PEM, zarówno na poziomie wymagań europejskich, jak i polskich. Scharakteryzowano wymagania zapisane w rozporządzeniu Ministra Środowiska z dnia 30 października 2003 r. odnoszące się do wartości dopuszczalnych poziomów PEM w środowisku i metod sprawdzania dotrzymania tych poziomów, jednocześnie wskazując na istotne różnice w stosunku do unijnego zalecenia 1999/519/EC. Szczegółowo omówiono sposoby wykonywania pomiarów PEM w środowisku, ze szczególnym uwzględnieniem pomiarów selektywnych częstotliwościowo w dziedzinie kodowej. Na koniec zwrócono uwagę na problem wyznaczania poziomów PEM w sieciach 5G
Underwater Acoustic Sensor Node Scheduling using an Evolutionary Memetic Algorithm, Journal of Telecommunications and Information Technology, 2018, nr 1
Get PDFUnderwater Acoustic Sensor Networks (UWASNs) play an important role in monitoring the aqueous environment which has created a lot of interest for researchers and scientists. Utilization of underwater acoustic sensor node (UASN) scheduling for transmission remains, due to the limited acoustic bandwidth available, a challenge in such an environment. One of the methods to overcome this problem is to efficiently schedule UASN data using time division multiple access (TDMA) protocols the parallel transmissions, simultaneously avoiding interference. The paper shows how to optimize the utilization of acoustic sensor node bandwidth by maximizing the possible node transmissions in the TDMA frame and also by minimizing the node's turnaround wait time for its subsequent transmissions by using an evolutionary memetic algorithm (MA). The simulation of MA-TDMA proves that as the size of the network increases, every node in UWASN transmits with an average minimal turnaround transmission time. It also proves that as the TDMA cycle repeats, the overall network throughput gets maximized by increasing the possible node transmissions in the MA-TDMA frame
Using Least Mean p-Power Algorithm to Correct Channel Distortion in MC-CDMA Systems, Journal of Telecommunications and Information Technology, 2018, nr 3
Get PDFThis work focuses on adaptive Broadband Radio Access Network (BRAN) channel identification and on downlink Multi-Carrier Code Division Multiple Access (MCCDMA) equalization. We use the normalized BRAN C channel model for 4G mobile communications, distinguishing between indoor and outdoor scenarios. On the one hand, BRAN C channel parameters are identified using the Least Mean p-Power (LMP) algorithm. On the other, we consider these coefficients in the context of adaptive equalization. We provide an overview and a mathematic formulation of MC-CDMA systems. According to these fundamental concepts, the equalizer technique is investigated analytically to compensate for channel distortion in terms of the bit error rate (BER). The numerical simulation results, for various signal-to-noise ratios and different p threshold, show that the presented algorithm is able to simulate the BRAN C channel measured with different accuracy levels. Furthermore, as far as the adaptive equalization problem is concerned, the results obtained using the zero-forcing equalizer demonstrate that the algorithm is adequate for some particular cases of threshold p
Low Density Parity Check Codes Constructed from Hankel Matrices, Journal of Telecommunications and Information Technology, 2018, nr 3
Get PDFIn this paper, a new technique for constructing low density parity check codes based on the Hankel matrix and circulant permutation matrices is proposed. The new codes are exempt of any cycle of length 4. To ensure that parity check bits can be recursively calculated with linear computational complexity, a dual-diagonal structure is applied to the parity check matrices of those codes. The proposed codes provide a very low encoding complexity and reduce the stored memory of the matrix H in which this matrix can be easily implemented comparing to others codes used in channel coding. The new LDPC codes are compared, by simulation, with uncoded bi-phase shift keying (BPSK). The result shows that the proposed codes perform very well over additive white Gaussian noise (AWGN) channels
Outage Performance of Bidirectional Full-Duplex Amplify-and-Forward Relay Network with Transmit Antenna Selection and Maximal Ratio Combining, Journal of Telecommunications and Information Technology, 2018, nr 1
Get PDFIn this paper, a bidirectional full-duplex amplify- and-forward (AF) relay network with multiple antennas at source nodes is proposed. Assuming that the channel state information is known at the source nodes, transmit antenna selection and maximal ratio combining (MRC) are employed when source nodes transmit information to the relay node and receive information from the relay node respectively, in order to improve the overall signal-to-interference plus noise ratio (SINR). Analytical expressions are derived for tight upper bound SINR at the relay node and source nodes upon reception. Further, losed form expressions are also derived for end-to-end outage probability of the proposed bidirectional full-duplex AF relay network in the Nakagami-m fading channel environment. Although self-interference at the relay node limits the performance of the full-duplex network, the outage performance of the proposed network is better than that of conventional bidirectional full-duplex and half-duplex AF relay networks, due to the selection diversity gain in TAS and diversity and array gain in MRC
