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Introduction
Marghescu Ion currently works at the Department of Telecommunications, Polytechnic University of Bucharest. Their current project is 'Cognitive approaches for location in mobile environments (CALM)'.
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Publications
Publications (84)
Recently, driver inattention has become the leading cause of automobile accidents. As a result, the driver's perception and decision-making abilities are diminished, and the driver can lose control of the car. To prevent accidents caused by driver inattention, it's vital to continuously monitor the driver and his driving behaviour and inform him if...
Nowadays, the flexible localization solution for various devices for work safety is one of the most demanding research questions. Notably, it is expected to provide an acceptable level of precision in different types of environments empowered by wearable technology and the Interent of Things (IoT) devices. Existing leading localization technologies...
Modern outdoor localization is commonly dependent on various Global Navigation Satellite Systems (GNSSs). On the other hand, they are known to be power-hungry and not suitable for resource-constrained devices currently flooding the Industrial Internet of Things (IIoT). Nonetheless, some of those devices may be equipped with Low-Power Wide-Area Netw...
With the decrease in the cost and size of drones in recent years, their number has also increased exponentially. As such, the concerns regarding security aspects that are raised by their presence are also becoming more serious. The necessity of designing and implementing systems that are able to detect and provide defense actions against such threa...
This work is a data descriptor paper for measurements related to various operational aspects of LoRaWAN communication technology collected in Brno, Czech Republic. This paper also provides data characterizing the long-term behavior of the LoRaWAN channel collected during the two-month measurement campaign. It covers two measurement locations, one a...
Today, ensuring work safety is considered to be one of the top priorities for various industries. Workplace injuries, illnesses, and deaths often entail substantial production and financial losses, governmental checks, series of dismissals, and loss of reputation. Wearable devices are one of the technologies that flourished with the fourth industri...
The present paper studies 5G challenges, requirements and key differentiating characteristics from the perspective of a Romanian mobile operator. The main contribution is that we created a vision about the use cases, physical and logical architecture needed to support these uses cases and other key differentiated factors, that the deployment of a f...
The performance of Wireless Sensor Networks (WSNs) faces a number of challenges. Of these challenges, energy consumption is considered a hot research area. Most WSN energy is used in transmitting the data from the sensor nodes either among each other or to a Base Station (BS). For this reason, many routing protocols have been developed to facilitat...
The present paper studies the main characteristics of digital radio relays used by the largest mobile network operator (MNO) in Romania in order to develop a network supporting the newest technologies available on the market. The main contribution is the design of a high capacity Ethernet radio relay network in an area around Bucharest, Romania. Th...
Low Energy Adaptive Clustering Hierarchy (LEACH) protocol is considered as one of the most important protocols that are frequently used in the Wireless Sensor Network (WSN). Many protocols were developed to modify and improve the LEACH protocol. The multi-hop technique (MHT-LEACH) is one of these protocols, which appeared to improve the performance...
As the evolution of wireless mobile communication in the last decades was an exponential one, a correct radio planning for each of the different existing standards became an essential aspect, in order to optimize the physical layer performance and minimize interferences. Several radio propagation models were designed in order to evaluate the radio...
Wi-Fi offloading allows the data traffic, coming from users of smartphones and tablets from congested areas of the 3G/HSDPA network, to be routed over a Wi-Fi network according to certain QoS and congestion parameters. In this paper a way to implement a 3G Wi-Fi offload solution in a cellular network is analyzed. Three offload algorithms that were...
Large scaled Multi-User Multi-Input-Multi-Output (MU-MIMO) wireless communication systems referring to a Base Station (BS) equipped with very large number of antennas (users) gain very high performance consideration due to high data rates, spectral efficiency and reliability that they can achieve. In multi-user wireless communication system with in...
The increasing demand for wide bandwidth wireless communication in the context of a finite available frequency spectrum has led to an acute need for spectrum-efficient technologies. One solution is the Cognitive Radio approach, a device aware of the environment and able to modify its own parameters accordingly in order to optimize the performance....
One of the critical challenges for mobile operators is how to approach the problem of the anticipated increase in traffic. A solution to this growth involves providing more throughput on the transmission path. One of the ways this can be done is to use LTE-Advanced with the carrier aggregation technique. With this feature we can allocate radio spec...
In this paper we present a Software-Defined Radio approach for an Electric Arc locator system. The core of the proposed hardware implementation is the USRP (Universal Software Radio Peripheral) development platform. The novelty of this work lies in the application of telecommunication specific advanced signal processing methods in the field of ener...
Many spectrum sensing algorithms have as a purpose determining if the primary users (PUs) are present or absent, by using statistical signal characteristics. However, for a better management of a cognitive network, additional information about PUs, such as their position, is required. Motivated by these requirements, this paper investigate the perf...
This paper presents two configurable radio implementations for an Electric Arc locator system. The novelty of the work lies in the application of the Software Radio and Software Defined Radio architecture and telecommunication specific signal processing algorithms for the field of energy generation and transmission. The advantage of the proposed so...
This paper presents a method for improving Angle-of-Arrival estimation accuracy in multipath environments using a sliding antenna array consisting of only two antennas. The proposed method is then experimentally validated by means of a dual channel Software-Defined Radio receiver and a wireless microphone.
One of the most important benefits of Multiple-Input Multiple-Output (MIMO) systems to multi-user (MU) scenarios seems to consist in achieving high data rate useful for future cellular systems. In order to eliminate interference in MU-MIMO systems, a number of low-complexity interference aware type of receivers were proposed. In this paper an enhan...
This paper presents a Software Radio implementation for an Electric Arc locator system. The novelty of this work resides in the application of telecommunication specific signal processing methods for the field of energy generation and transmission. The advantage of the proposed solution compared to other current implementations is the improved flex...
This paper presents a Software Radio implementation for a system capable of locating unintentional ozone-generating sources. Arc discharges produced by electric equipment are a major ozone generator in industrial-related environments. There is evidence that long term exposure to ozone is a serious health threat. The novelty of this work resides in...
The paper presents a new high-efficiency power switching supply using the Gallium Nitride (GaN) technology. There are compared two solutions, the first using standard MOS transistors and the second using the new GaN transistor. The actual green technologies for obtaining the maximum energy and minimum losses have pushed the semiconductor industry i...
Many applications have been developed or are under development in the areas of environmental monitoring, detecting construction malfunctions of smart houses, and tracking targets. These applications require a good orientation of the nodes relative to a global reference system in order to provide geographical information that is very important. In t...
Spectrum scarcity became a serious problem in
recent years, due to the multitude of communication systems
requiring frequency resources. Cognitive Radio (CR) technology
offers a solution by allowing unlicensed users to access licensed
frequency bands. Any CR equipment should perform a spectrum
sensing process in order to detect the presence of...
Cognitive radio (CR) technology promises to offer viable solutions to address the problem of limited spectrum resources availability. One key element in CR functionality is being able to perform dynamic spectrum access, as it offers the possibility for unlicensed users to access unoccupied licensed frequency bands. For cognitive networks to operate...
The high demand for radio resources that became critical in the last years leaded to a reconsideration of the way in which the frequency spectrum is used. The classical method of allocating resources is a static one, as the licenses for most of the frequency bands are sold for long periods of time and give exclusive rights to the owner. By using su...
Multiple-Input Multiple-Output (MIMO) systems offer considerable increase in data throughput and link range without additional bandwidth or transmit power by using several antennas at transmitter and receiver to improve wireless communication system performance. At the same time, Orthogonal Frequency Division Multiplexing (OFDM) has becoming a very...
The paper investigates and compares two different solutions to improve a printed circuit board designed for a portable computer main board. The issue represents the analog circuits and switching power supplies. The main example is a simple analog circuit, low dropout regulator (LDO), integrated into a complex analog circuit. The LDO stability versu...
This paper investigate the effect of transmit diversity in LTE downlink transmission. Transmit diversity scheme known as Space Frequency Block Codes (SFBC) is considered. As performances metrics, the average BER is evaluated in terms of signal to interference-plus-noise ratio (SINR). We evaluate the channel estimation scheme for LTE downlink based...
A charged particle which travels a dielectric medium with a velocity greater than the light one will generate Cherenkov radiation in a wide range of frequencies. In this paper we presented a model and a possible implementation of a cosmic radiation detector that can detect particles, like neutrinos. The model is evaluated in salt mines, because thi...
In order to enable the coexistence of an ever-increasing number of communication systems in a limited amount of frequency, the traditional static frequency allocation is not the best solution any longer. Cognitive Radio (CR) technology, based on a dynamic spectrum access, is a possible solution for improving the efficiency of spectrum usage. A firs...
This paper presents a novel solution for reducing the peak current and the Electro-Magnetic Interference (EMI) even if the circuit is located in the pack cells or on the motherboard. The software algorithm and the hardware solution were developed respecting the actual standards and rules regarding the battery chemistry, power saving requirements an...
The Integrated Circuits Characterization Platform (ICCP) is an automated measuring tool which offers more flexible and higher accuracy measurements on the new fabricated IC's. This platform is intended to be used with a PCB named “demo board”, which includes the socket for the desired IC and minimum external components. With few modifications, the...
TV White Spaces (TVWS) are becoming more and more attractive for deploying high-speed broadband wireless communications in the freed spectrum left from the analog switchoff (ASO). In this respect, dynamic spectrum access (DSA) procedures are critical and have to rely on very accurate spectrum sensing techniques. This paper provides an overview of t...
Experimental analysis of dielectric properties of the salt and electromagnetic wave propagation trough salt ore can provide opportunities for a small astronomical observatory in a salt mine in Romania. Cherenkov radiation (generated by neutrinos) detection threshold is very low for the salt, and represents half of the ice one. Electromagnetic waves...
Global Navigation Satellite Systems (GNSS) systems share the same spectrum with other telecommunication systems. Papers based on actual RF measurement campaigns have reported that loss-of-lock on the navigational signals can happen to unaided GNSS receivers near radio and TV broadcast transmitters [5]. Radionavigation and communication systems can...
In this article the effect of LTE network time synchronization in local area network has been investigated. We considered an indoor office scenario. The investigation is conducted by means of a LTE system-level simulator. The simulator is offered for free under an academic, noncommercial use license. Long Term Evolution (LTE) is a cellular technolo...
This paper investigates the effect of SINR in LTE downlink transmission. 3GPP Long Term Evolution (LTE) is the evolution of the Universal Mobile Telecommunications System (UMTS) which will make possible to deliver next generation high quality multimedia services according to the users' expectations. The results of this simulation serves to evaluate...
Nowadays, location-enabled mobile phones are becoming more and more widespread. Various players in the mobile business forecast that, in the future, a significant part of total wireless revenue will come from Location-Based Services (LBS). An LBS system extracts information about the user’s geographical location and provides services based on the p...
RAKE receiver is a digital receiver that takes advantage of temporal diversity of a multipath channel in order to increase the average received signal to noise ratio (SNR). In this paper we will analyze the performances of RAKE receiver for ultra wideband system with pulse amplitude modulation and time hopping spreading technique. These ultra wideb...
In this paper we address the issue of multipath propagation of the Galileo CBOC signal, using carrier phase investigation approaches. While the multipath estimation problem has been widely addressed, the multipath detection has not been so much investigated so far, especially with Galileo signals. The detection of the multipath propagation situatio...
Location Based Services (LBS) are nowadays recognized as having one of the most fast-paced developments in the wireless field. The underlying location technology is still mainly based on the Global Navigation Satellite Systems (GNSS), but many complementary technologies, such as cellular-based location, WLAN-based location and other Signal of Oppor...
Galileo, the future European GNSS, is planning to transmit navigation signals in four sub-bands (E5a, E5b, E6 and E1) within the L band. There are also other applications which use the L band worldwide, sharing the spectrum with GNSS or utilizing neighboring bands. Reports of measurement campaigns have shown that unaided GNSS receivers could experi...
Satellite-based positioning is nowadays experiencing an exponential growth of the consumer segment demand and the Global Positioning System (GPS) is the main provider of this service. While GPS performs very well in outdoor conditions, many people still cannot be located when they are in indoor environment. The characteristics of the indoor propaga...
Inefficient usage of the radio frequency spectrum has been identified as one of the major problems to be solved, in a world where new communication systems appear more often lately than ever before. Cognitive Radio (CR) technology promises to be one possible solution to this problem, by allowing access of unlicensed users in licensed bands, based o...
In this paper, phase shift keying–trellis coded modulation (PSK–TCM) schemes are designed using recursive convolutional encoders over Galois field GF(2N). These encoders are designed using the nonlinear left-circulate (LCIRC) function. The LCIRC function performs a bit left circulation over the representation word. Different encoding rates are obta...
In this paper, phase shift keying–trellis coded modulation (PSK–TCM) schemes are designed using recursive convolutional encoders over Galois field GF(2 N). These encoders are designed using the nonlinear left-circulate (LCIRC) function. The LCIRC function performs a bit left circulation over the representation word. Different encoding rates are obt...
In this paper, parallel turbo phase shift keying - trellis coded modulation (Turbo PSK-TCM) schemes are designed using recursive convolutional encoders over Galois field GF(2<sup>N</sup>). These encoders are designed using the nonlinear left-circulate (LCIRC) function. The LCIRC function performs a bit left circulation over the representation word....
Due to the ever-increasing number of radio communication technologies, lack of frequency spectrum has become a serious problem recently. Cognitive Radio (CR) technology promises to be one possible solution to this problem, by allowing access of unlicensed users in licensed bands, based on an opportunistic approach and without interfering with the l...
Lack of frequency spectrum is becoming one
of the major problems in the telecommunication field
with the introduction of several new radio
communication technologies. Cognitive Radio (CR)
technology promises to be one possible solution to this
problem, by allowing access of unlicensed users in
licensed bands, based on an opportunistic approach and...
In this paper, parallel turbo quadrature amplitude modulation - trellis coded modulation (Turbo QAM-TCM) schemes are designed using recursive convolutional encoders over Galois field GF(2 N). These encoders are designed using the nonlinear left-circulate (LCIRC) function. The LCIRC function performs a bit left circulation over the representation wo...
In this paper, optimum recursive systematic convolutional (RSC) encoders over Galois field GF(2<sup>N</sup>) are designed using a nonlinear function, i.e., left-circulate function (LCIRC). The LCIRC function performs a bit left circulation over the representation word; it is used in microprocessors as an accumulator operation, and in chaotic sequen...
This paper aims to present the results that can be obtained with a conventional multiuser detector used in conjunction with turbo encoding in order to improve its performance, evaluated in terms of bit error rate (BER) as a function of signal to noise ratio (SNR). We used extensive Monte Carlo simulations, taking into consideration different combin...
This paper investigates the chaos-based asynchronous direct sequence code-division multiple access (DS-CDMA) system performance optimization in accordance with spreading sequences set. The multiple access interference (MAI) power is estimated for conventional matched-filter receiver scheme, under the standard gaussian approximation (SGA) hypothesis...
The profound changes in society and dramatic development of technology have significant effects on the education who must face the challenges of the new century. This paper deals with one of the alternatives to the classical education technology: the m-learning. The particularities, the advantages, the disadvantages and the social impact of the m-l...
Acest îndrumar se doreşte a fi un sprijin în asimilarea noţiunilor de bază necesare cunoaşterii sistemelor de radiocomunicaţii. Lucrările se vor efectua atât prin măsurători directe, cât şi prin simulare, cu ajutorul mediului SIMULINK. Întrebările şi exerciţiile de la sfârşitul lucrărilor au ca scop fixarea noţiunilor teoretice prezentate.
Primele...
The communication process in spread spectrum and CDMA like systems requires PN families with good correlation properties. The research activity in this area was stimulated and many such families were developed: m-sequences, Gold, Kasami or OVSF (orthogonal variable spreading factor) codes. Some of them have been chosen to implement WCDMA mechanisms...
The ATHENA European Research project (FP6-507312) is proposing a specific structure of hybrid communications access network, exploiting the particularities of the DVB-T system in offering broadband connectivity to Internet for a large category of users. Based on this structure, a specific test-bed was implemented at Politehnica University of Buchar...
The initial search procedure in WCDMA is used to identify the scrambling code used by the base station that has the lowest path loss coefficient of the received signal, among all the other base stations. Before this action, the slot synchronization, frame synchronization and code-group identification must be performed. This paper deals with an opti...
Environment dependent propagation factors like time delay spread and pass loss have a determinant influence upon wireless communication systems engineering. These factors tend to become part of the wireless networks, so accurate determination methods are needed. A versatile sounding equipment based on convolution matched-filter method is presented...