Alexandru Martian

Polytechnic University of Bucharest | UPB

To enable emerging applications of fifth generation (5G) systems for vertical scenarios like mobile broadband and Internet of things (IoT) for vehicles and maritime sectors, a new trend towards softwarization and establishment of private networks is gaining momentum. Different from earlier generations of mobile systems where network functions are t...

Automating software orchestration and service development represents the newest trend in the development of fifth generation (5G) core network (CN) as it enables flexible and scalable service deployment. The building blocks for such a trend include Containers, Docker, Kubernetes, and other orchestration methods that facilitate easy scaling, managem...

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...

Energy detection (ED) represents a low complexity approach used by secondary users (SU) to sense spectrum occupancy by primary users (PU) in cognitive radio (CR) systems. In this paper, we present a new algorithm that senses the spectrum occupancy by performing ED in $K$ consecutive sensing time slots starting from the current slot and continuing...

Implementation of dynamic spectrum access (DSA) in cognitive radio (CR) systems requires the unlicensed secondary users (SU) to implement spectrum sensing to monitor the activity of the licensed primary users (PU). Energy detection (ED) is one of the most widely used methods for spectrum sensing in CR systems, and in this paper we present a novel E...

One of the practical solutions for space deployment of large-scale scientific instruments is satellite formation flying. In this type of space mission, several smaller satellites have the ability to interact and cooperate with each other via inter-satellite links (ISL) for tasks commonly performed by a larger and more complex satellite. Formation f...

One of the challenges of future space missions is the deployment of instruments distributed across multiple satellites that fly in an autonomous formation. This type of mission requires that the spacecraft communicate using inter-satellite links (ISL) and collaborate to fulfil the role of a large-scale, complex scientific instrument. In this contex...

In the context of the upcoming 5G networks, the current paper reviews several aspects regarding the New Radio (NR) physical layer: the radio technologies that were proposed for the implementation of the air interface, the frequency bands foreseen to be used and access in unlicensed spectrum areas. The current situation regarding the introduction of...

Even if the pesticides can cause different diseases, there are few methods to detect their influence and presence within the food products. However, it has been found a way to detect these harmful substances. The use of a potentiostat within a telemetry system can represent the solution to this problem. The potentiostat is an electronic device whic...

The goal of this paper is to set the optimal safety usability for wearable biosensors for patient monitoring. This objective consists in minimizing the security risks by using the adequate methodology for working with personal sensitive data, anonymization and data analytics in cloud. The possibility of use the data is to filter data in private clo...

As the lack of frequency resources became a critical problem in recent years, solutions had to be found in order to use the available spectrum in a more efficient way. Cognitive radio (CR) technology is a possible answer to this, by proposing a dynamic spectrum access approach, which allows unlicensed users to access unused licensed frequency bands...

Spectrum sensing is a crucial function required for an agile Cognitive Radio (CR) user. The simplest solution for CR spectrum sensing is provided by Energy Detection (ED) algorithms due to their independence on the Primary User (PU) signal's characteristics. Recently, we proposed an ED algorithm, which decides on the PU signal presence considering...

An energy detection (ED) algorithm, which takes into consideration three consecutive sensing events, is introduced in this letter. This algorithm, named three-event ED (3EED), takes the decision in one sensing event, considering also the event immediately before and the one immediately after it. We design the proposed algorithm to exploit the knowl...

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...

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...

Big data storage and processing are considered as one of the main applications for cloud computing systems. Furthermore, the development of the Internet of Things (IoT) paradigm has advanced the research on Machine to Machine (M2M) communications and enabled novel tele-monitoring architectures for E-Health applications. However, there is a need for...

In this paper, a comparative study between the results of a measurement campaign conducted in northern Greece and simulations performed with Radio Mobile and ICS Telecom radio planning tools is performed. The DVB-T coverage of a transmitting station located near the city of Thessaloniki is estimated using three empirical propagation models (NTIA-IT...

As the demand for frequency resources increases because of the great number of new wireless technologies, the frequency spectrum becomes overcrowded and solutions have to be found in order to solve this problem. One possible solution would be to take advantage of the so called white spaces (WS), frequency bands that are actually not used by the pr...

Hydro-, Aeolian and Solar energy show significant promise in helping to reduce pollutants and greenhouse gases, which is a primary focus in today’s sustainable development culture. To enjoy the power of them, the human society needs solutions to transform the energies mentioned above into electric energy, at specific reliability, efficiency and sus...

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...

Cognitive radio (CR) technology promises to be one possible solution to address the lack of spectrum resources. The dynamic spectrum access approach is one of the key elements of CR, as it allows unlicensed users to access unused licensed frequency bands. In order to detect the presence of licensed users, one of the main tasks that a CR equipment h...

The increased number of wireless communication systems in the last decades raised the problem of the limited resources in the frequency domain. Cognitive Radio (CR) technology, based on a dynamic spectrum access (DSA), is a possible solution for improving the efficiency of spectrum usage. A necessary step in order to identify suitable frequency...

With Cloud computing increasingly adopted for different applications, it is hard sometimes to analyze the performance of novel planning and resource allocation algorithms on real test systems in the Cloud. At the same time, simulation tools allow researchers to quickly evaluate new algorithms using heterogeneous infrastructures like the Cloud. To p...

Spectrum scarcity has become one of the most important problems to be solved in order to ensure the coexistence of the large number of modern communication systems. Cognitive radio (CR) technology has been considered a promising solution for enabling dynamic spectrum access and by that addressing this problem. Since its inception more than 10 years...

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...

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...

In this paper we propose a new detector for the spatial modulation (SM) receiver. In trellis coded spatial modulation (TCSM) schemes, the joint detection is used for identifying both the antenna index and the transmitted symbol. We define a hybrid maximum-likelihood (ML) SM detector, which determines the transmit antenna index soft estimate and the...

Conforming to european standards, starting with the 1st of January 2012 analog TV broadcasting should be completely replaced by digital broadcasting in Romania. In this paper we present a series of measurements done in the 470-790 MHz band, which for the moment still contains both old analog TV stations and new digital ones. An analysis is being ma...

Recently, a new family of recursive systematic convolutional (RSC) encoders over Galois field GF ( 2N ) was introduced. The present paper considers the parallel turbo trellis coded modulation (TTCM) scheme using these nonbinary encoders as constituent codes. Besides operating over a higher order Galois field, these encoders use a non-linear functio...

In the latest years multiuser detection systems have supported an increase in design, capacity and performances. Their complex structure requires attention in the process of choosing the appropriate parameters. In CDMA (Code Division Multiple Access) system very important roles in achieving significant performances are played by the power of the si...

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...

The present paper is analysing the occupancy of the radio spectrum for some typical CDMA communications systems. The paper presents also an analysis of how the available channel are used by the communications system and especially of how other available channels could be detected. As example, the paper presents also how the IMT-2000 uplink bands ca...

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...