Institute of Electron Technology
Biblioteka Cyfrowa Instytutu Łączności / National Institute of Telecomunications: Digital LibraryNot a member yet
2189 research outputs found
Sort by
Performance Evaluation of MC-CDMA Systems with Single User Detection Technique using Kernel and Linear Adaptive Method, Journal of Telecommunications and Information Technology, 2021, nr 4
Full text linkAmong all the techniques combining multi-carrier modulation and spread spectrum, the multi-carrier code division multiple access (MC-CDMA) system is by far the most widely studied. In this paper, we present the performance of the MC-CDMA system associated with key single-user detection techniques. We are interested in problems related to identification and equalization of mobile radio channels, using the kernel method in Hilbert space with a reproducing kernel, and a linear adaptive algorithm, for MC-CDMA systems. In this context, we tested the efficiency of these algorithms, considering practical frequency selective fading channels, called broadband radio access network (BRAN), standardized for MC-CDMA systems. As far as the equalization problem encountered after channel identification is concerned, we use the orthogonality restoration combination (ORC) and the minimum mean square error (MMSE) equalizer techniques to correct the distortion of the channel. Simulation results demonstrate that the kernel algorithm is efficient for practical channel
High Temperature Effects in Fused Silica Optical Fibers, Journal of Telecommunications and Information Technology, 2021, nr 3
Full text linkFire-resistant fiber optic cables used in safety and monitoring systems playing an essential role in fire fighting and building evacuation procedures are required to temporarily maintain optical continuity when exposed to fire. However, the use of fused silica fiber at temperatures between 800◦C and 1000◦C is associated with two highly undesirable phenomena. Thermal radiation (incandescence) of optical fibers, with its intensity and spectral distribution being proportional to additional attenuation observed in the fiber’s hydroxyl absorption bands (“water peaks”) is one of them. The other consists in penetration of thermal radiation from the surroundings into the fiber, due to defects in glass, causing light scattering and resulting in fiber brittleness. Thermal radiation is a source of interference in fiber attenuation measurements performed during fire tests and affects normal operation of fiber optic data links in the event of a fire. In this article, results of laboratory tests performed on a telecom single mode and multimode fibers subjected to temperatures of up to 1000◦C are presente
Linear and Planar Array Pattern Nulling via Compressed Sensing, Journal of Telecommunications and Information Technology, 2021, nr 3
Full text linkAn optimization method based on compressed sensing is proposed for uniformly excited linear or planar antenna arrays to perturb excitation of the minimum number of array elements in such a way that the required number of nulls is obtained. First, the spares theory is relied upon to formulate the problem and then the convex optimization approach is adopted to find the optimum solution. The optimization process is further developed by using iterative re-weighted l1- norm minimization, helping select the least number of the sparse elements and impose the required constraints on the array radiation pattern. Furthermore, the nulls generated are wide enough to cancel a whole specific sidelobe. Simulation results demonstrate the effectiveness of the proposed method and the required nulls are placed with a minimum number of perturbed elements. Thus, in practical implementations of the proposed method, a highly limited number of attenuators and phase shifters is required compared to other, conventional method
Evaluation of Radio Channel Utility using Epsilon-Greedy Action Selection, Journal of Telecommunications and Information Technology, 2021, nr 3
Full text linkThis paper presents an algorithm that supports the dynamic spectrum access process in cognitive radio networks by generating a sorted list of best radio channels or by identifying those frequency ranges that are not in use temporarily. The concept is based on the reinforcement learning technique named Q-learning. To evaluate the utility of individual radio channels, spectrum monitoring is performed. In the presented solution, the epsilon-greedy action selection method is used to indicate which channel should be monitored next. The article includes a description of the proposed algorithm, scenarios, metrics, and simulation results showing the correct operation of the approach relied upon to evaluate the utility of radio channels and the epsilon-greedy action selection method. Based on the performed tests, it is possible to determine algorithm parameters that should be used in this proposed deployment. The paper also presents a comparison of the results with two other action selection method
5G New Business Opportunities – New Business Models, Pricing, and Use Cases, Journal of Telecommunications and Information Technology, 2021, nr 2
Full text linkThis paper addresses how network operators may gain a reasonable return on their investment into 5G infrastructure. It first considers the 5G mobile network costs structure then applies this to three typical use case
Artificial Magnetic Conductor-based Millimeter Wave Microstrip Patch Antenna for Gain Enhancement, Journal of Telecommunications and Information Technology, 2021, nr 1
Full text linkIn this paper, a small (20 × 20 × 2.4 mm) loaded microstrip patch antenna (MPA) with an asymmetric artificial magnetic conductor (AMC) as a ground plane is designed for millimeter wave applications. Two AMC structures are proposed; one has the property of a 0 ◦ reflection phase around 28.4 GHz, with a symmetric geometry, which makes the reflection phase insensitive to variations in both polarization and incident angle. This symmetric AMC structure ensures angular stability which is considered as a major requirement when periodic structures are used as antenna ground planes. The other structure is characterized by an asymmetric geometry and shows an interesting behavior around 28.6 GHz, where a discontinuity in the reflection phase appeared due to the fact that surface impedance nature changed from purely capacitive to purely inductive. This paper studies the effects of the two proposed AMC structures on the performance of MPAs, by using an array of 8 × 8 unit cell elements as an artificial ground plane. Simulation results show that an MPA with a symmetric AMC ground plane offers better impedance matching and a wider bandwidth. Compared with conventional MPAs, gain is enhanced and directivity is improved as well. As far as an MPA with an asymmetric AMC ground plane is concerned, its performance in terms of gain and directivity is higher than that of the conventional solution
5G Is Out There: How to Ride the Market Storm and Thrive, Journal of Telecommunications and Information Technology, 2021, nr 2
Full text linkWe examine the changes in the commercial model adopted by the mobile ICT industry, due to the advent of 5G technology. This includes consideration of the challenges involved in rolling out a new infrastructure, which new markets this is likely to open up and how this affects partnering decisions. We show that as technology horizons expand, their degree of overlap increases and previously complimentary technologies may compete with each other, impacting the size of the addressable market. It is expected that 5G, whilst supporting its existing markets, will offer additional machine to machine, low latency and highly reliable services. We consider the synergies and the drivers for adoption for the wider 5G propositions and consider the impetus for more bandwidth and services and how the new technology impacts selling approaches. We identify the risks and uncertainties for the network providers and the likely requirements for a sustainable 5G business model and will describe our view of the steps necessary for a 5G successful outcom
Performance Analysis of Filtered OFDM Based Downlink and Uplink NOMA System over Nakagami-m Fading Channel, Journal of Telecommunications and Information Technology, 2021, nr 2
Full text linkEfficient consumption of available resources and fulfillment of increasing demands are the two main challenges which are addressed by exploring advanced multiple access schemes along with efficient modulation techniques. To this end, non-orthogonal multiple access (NOMA) is discussed as a promising scheme for future 5G traffic. NOMA enables the users to share same resource block, permitting certain level of interference. In this paper, we propose filtered OFDM (F-OFDM) as a transmission waveform for NOMA systems, as it offers all the advantages of OFDM with the additional provision of sub-band filtering to satisfy the diverse services of the users. We examine F-OFDM in both downlink and uplink NOMA systems. Error-related performances of both downlink and uplink F-OFDM NOMA systems are analyzed and compared with conventional OFDM NOMA system over Nakagami-m fading channel. The results show that the error performance of F-OFDM NOMA is better than that of OFDM NOMA. An improvement of about 2 dB and 1 dB in bit error rate is achieved in downlink and uplink F-OFDM NOMA, respectively. Monte Carlo simulations are conducted for different values of fading parameter m, supporting the obtained analytical result
Digital Predistortion of Wideband Signals with Reduced Complexity Based on Feedback Wiener System, Journal of Telecommunications and Information Technology, 2021, nr 2
Full text linkDigital predistortion (DPD) using baseband signals is commonly used for power amplifier linearization. This paper is devoted to this subject and aims to reduce DPD complexity. In this study, we propose a structure that allows to decrease the number of DPD parameters by using multiple blocks, with each one of them dedicated to characterizing the non-linear behavior and/or memory effects. Such a structure is based on the feedback Wiener system, involving a FIR filter used as a feedback path to reproduce the PA inverse dynamics. A memory polynomial block (MP) is inserted as the final element to minimize the modeling errors. A relevant model identification method, based on an iterative algorithm, has been developed as well. The proposed architecture is used for the linearization of a commercial class-AB LDMOS RF PA by NXP Semiconductors, in wideband communication systems. Comparison of performance with the conventional generalized memory polynomial model (GMP) shows that the proposed model offers similar results, with its advantage consisting in the reduced number of parameters