In this paper, a novel transmission strategy for Mutliple Input Multiple Output Wideband Code Div... more In this paper, a novel transmission strategy for Mutliple Input Multiple Output Wideband Code Division Multiple Access (MIMO-WCDMA) orientations operating in frequency-selective fading environments is investigated, in terms of overall algorithmic complexity reduction. To this end, Principal Component Analysis (PCA) is employed on the received data matrix, in order to define the significant terms that are taken into account during transmission matrix formulation. According to the presented results, feedback information of only the primary eigenvector of the corresponding covariance matrix of the received data matrix is required, in order to maintain the mean Bit Error Rate (BER) at acceptable levels. In particular, a complexity reduction of up to 10% can be achieved, when comparing BER values derived by the selection of all components of the received covariance matrix during transmission matrix formulation, and the corresponding BER when selecting half of the components. This reducti...
Phased array antennas are a viable solution to a number of problems related to radio communicatio... more Phased array antennas are a viable solution to a number of problems related to radio communications applications. In this work, the multi-objective stochastic MOPSO algorithm is used to optimize the spatial configuration of a symmetric phased linear array. The defined optimization goals were the suppression of the radiation pattern sidelobes at a specified maximum scan angle as well as the minimization of the induced voltages correlation at the receiver frontend in order to maximize diversity performance. Non-linear constraints were enforced on the solution set, related to the multi-antenna system aperture efficiency and related to the mismatching when the array is scanned. The obtained optimized configurations for an array composed of 16 dipoles resulted in reducing the sidelobes up to 2.5 dB, when scanned 60 • away from broadside, compared to a linear array with elements spaced λ/2 apart. Furthermore, the optimized dipole arrays were characterized by a maximum element correlation of 0.12 to 0.43. The performance of obtained configurations was shown to be tolerant to feed phase variations that appear in realistic implementations. The arrays were analyzed employing the Method of Moments (MoM).
An approach based on acoustics and its theoretical analogies to electromagnetism is used in the p... more An approach based on acoustics and its theoretical analogies to electromagnetism is used in the present research to study the detection of the acoustic wave energy radiated by the thermal random motion of material particles of the brain during activation or caused by pathology. Pressure and particle velocity are calculated in analytical mathematical forms for the case of human brain monitoring, which can be implemented by a prototype passive acoustic brain monitoring system (PABMOS). A sphere to model the human head and an internal point source in order to simulate potential pressure alterations due to intracranial abnormalities or local functional activations, are used in the theoretical representation of the present approach. Finally, numerical results for arbitrary positions of the internal source, concerning the particle velocity (pressure field distribution) at the surface of the head model which can implicitly be measured by the suitable piezoelectric sensors, are presented.
ABSTRACT Convergence proposes the enhancement of the Internet with a novel, content-centric, publ... more ABSTRACT Convergence proposes the enhancement of the Internet with a novel, content-centric, publish–subscribe service model based on the versatile digital item (VDI): a common container for all kinds of digital content, including digital representations of real-world resources. VDIs will serve the needs of the future Internet, providing a homogeneous method for handling structured information, incorporating security and privacy mechanisms. CONVERGENCE subsumes the following areas of research: · definition of the VDI as a new fundamental unit of distribution and transaction; · content-centric networking functionality to complement or replace IP-address-based routing; · security and privacy protection mechanisms; · open-source middleware, including a community dictionary service to enable rich semantic searches; · applications, tested under real-life conditions.
The terrestrial digital video broadcasting (DVB-T) network planning is the main interest of this ... more The terrestrial digital video broadcasting (DVB-T) network planning is the main interest of this article along with a case study for Greece. The basic principles and the guidelines of the DVB-T planning process are presented in conjunction with their application to the establishment of the Greek DVB-T allotment plan. The procedures described in this article were followed by the authors during the International Telecommunication Union (ITU) DVB-T planning project that concluded with the ITU's Regional Radiocommunication Conference 2006 (RRC-06) and the Geneva (GE-06) frequency plan for terrestrial digital radio broadcasting.
ABSTRACT Convergence proposes the enhancement of the Internet with a novel, content-centric, publ... more ABSTRACT Convergence proposes the enhancement of the Internet with a novel, content-centric, publish–subscribe service model based on the versatile digital item (VDI): a common container for all kinds of digital content, including digital representations of real-world resources. VDIs will serve the needs of the future Internet, providing a homogeneous method for handling structured information, incorporating security and privacy mechanisms. Convergence subsumes the following areas of research: · definition of the VDI as a new fundamental unit of distribution and transaction; · content-centric networking functionality to complement or replace IP-address-based routing; · security and privacy protection mechanisms; · open-source middleware, including a community dictionary service to enable rich semantic searches; · applications, tested under real-life conditions.
ITST 2007 - 7th International Conference on Intelligent Transport Systems Telecommunications, Proceedings, 2007
The purpose of the study presented in this paper is to investigate the performance of a multicell... more The purpose of the study presented in this paper is to investigate the performance of a multicelluar Wideband Code Division Multiple Access (WCDMA) network for different multiuser detection (MUD) strategies in terms of maximum achievable capacity. Capacity is evaluated both with system level simulations for different loading, as well as with link level simulations for different MUD techniques. Due to
2007 16th IST Mobile and Wireless Communications Summit, 2007
ABSTRACT This paper presents an adaptive admission control (AC) strategy for wideband code-divisi... more ABSTRACT This paper presents an adaptive admission control (AC) strategy for wideband code-division multiple access (WCDMA) cellular networks which employ antenna arrays (AAs) at the base station (BS). The AAs are either used to form a fixed grid of beams, or to steer beams in the directions of groups of users. The adaptive AC strategy maximizes the cell throughput in a multirate environment by grouping as many users as possible under a common beam formed by the AA, taking into account their spatial distribution. A WCDMA semi static simulator is used to evaluate the proposed algorithm for different traffic scenarios, by means of Monte Carlo (MC) simulations. Results indicate that the network with the adaptive AC can achieve almost two times higher throughput per beam compared to the traditional AC in a multirate cellular environment with hot spot areas.
The goal of the study presented in this paper is to investigate the performance of a WCDMA multic... more The goal of the study presented in this paper is to investigate the performance of a WCDMA multicellular network which employs antenna arrays (AAs) at the base station (BS) under different Radio Resource Management (RRM) strategies. The performance is evaluated statistically in terms of maximum achievable capacity. A WCDMA system level simulator has been developed which executes independent Monte Carlo (MC) simulations in parallel. Simulation results indicate that there can be significant variations in capacity resulting from the differences in the interference suppression mechanism among the RRM strategies.
The goal of the study presented in this paper is the accurate performance evaluation of adaptive ... more The goal of the study presented in this paper is the accurate performance evaluation of adaptive beam-centric admission control (AC) for wideband code-division multiple access (WCDMA) multicell networks with non-uniform traffic requirements. Each NodeB employs antenna arrays (AAs), used either to form fixed grids of beams (FGoBs), or to steer and shape multiple beams towards directions of increased traffic, in an adaptive manner. The adaptive beam-centric AC maximizes the cell throughput in a multirate/multicell environment by grouping as many users as possible under a common beam formed by the AA, taking into account their spatial distribution and overall interference. Due to the increased complexity of the Monte Carlo (MC) simulations, a novel grid-enabled problem solving environment has been developed in order to reduce execution times considerably and make feasible full scale extensive simulations of complex operational scenarios (up to 4 tiers of cells, multiple beams per cell, non-uniform traffic distributions with different spatial characteristics). Results show that the network with the adaptive beam-centric AC can achieve significantly higher throughput per beam in multirate/multicell environments with hotspots. In particular, it is shown that the throughput per beam gain depends exponentially on the
Wireless Communications and Mobile Computing, 2013
This paper investigates the performance of different transmission strategies for multiple input m... more This paper investigates the performance of different transmission strategies for multiple input multiple output (MIMO) networks with the wideband code division multiple access (WCDMA) air interface as the physical layer protocol. Performance is evaluated statistically with extended Monte Carlo (MC) simulations in terms of achievable bit-error (BER) rate in frequency selective fading cellular environments. As results indicate, for a MIMO configuration with M t antennas at the base station (BS), M r antennas per mobile station (MS) and L resolvable multipath components, the transmission strategy based on signal to noise ratio (SNR) enhancement is the optimum transmit solution for M t ≤ M r . However, the pre-RAKE maximal ratio combining transmission strategy outerperforms the SNR enhancement strategy with post-RAKE processing for M t > M r , high number of resolvable multipath components and channel estimation error up to 40%. Moreover, a transmission scheme based on the maximization of the ratio of the desired MS's signal to the total amount of interference that causes to the network is proposed, and is shown that outerperforms the conventional transmission schemes for high data rate services. For symmetric MIMO configurations (M t = M r ) and two resolvable multipath components, this strategy provides 30% BER gain compared to the maximization of SNR strategy. This gain can be further improved by 25% with a proposed adjacent sector cooperation algorithm.
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Papers by P. Gkonis