Panagiotis K. Gkonis

A new subcarrier allocation strategy for MIMO-OFDMA multicellular networks based on cooperative interference mitigation.

The goal of the study presented in this paper is to investigate the performance of a new subcarrier allocation strategy for Orthogonal Frequency Division Multiple Access (OFDMA) multicellular networks which employ Multiple Input Multiple Output (MIMO) architecture. For this reason, a hybrid system-link level simulator has been developed executing independent Monte Carlo (MC) simulations in parallel. Up to two tiers of cells around the central cell are taken into consideration and increased loading per cell. The derived results indicate that this strategy can provide up to 12% capacity gain for 16-QAM modulation and two tiers of cells around the central cell in a symmetric 2 × 2 MIMO configuration. This gain is derived when comparing the proposed strategy to the traditional approach of allocating subcarriers that maximize only the desired users signal.

Theoretical Analysis of a Passive Acoustic Brain Monitoring System

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 fleld distribution) at the surface of the head model which can implicitly be measured by the suitable piezoelectric sensors, are presented.

Resource management in OFDMA heterogeneous network

In this study, a Long Term Evolution Advanced (LTEa) - based multi-user Orthogonal Frequency Division Multiple Access (OFDMA) heterogeneous network has been simulated and a resource allocation strategy has been proposed. The strategy under consideration can inherently mitigate electromagnetic interference, hence increases the mean number of terminals, and requires no channel state information (CSI). To evaluate the performance of the network platform and the proposed strategy, the system is studied for different network orientations. According to the results, the platform is a good reality simulator, whereas owning to the proposed Radio Resource Management (RRM) algorithm the mean capacity can reach a 12-fold increase especially for highly noisy operating environments.

Low-complexity Anti-Jamming Subcarrier scavenging strategies for OFDMA networks

The goal of the study presented in this work is to evaluate the performance of OFDMA networks for different subcarrier allocation strategies. Considering no Channel State Information at the transmitter, two low-complexity subcarrier allocation strategies are employed so as to combat interference among inter-cell mobile subscribers and to judicious distribute power budget among them. In comparison to traditional allocation strategies, for 2/3/4/5 subcarriers per mobile subscriber and different permission ratios (10%, 30%, 40%), simulation results indicate that the proposed algorithms enhance the capacity (mean number of mobile subscribers) of the overall system. In some cases the capacity gain reaches 93.39%.

On the performance evaluation of two novel fractional frequency reuse approaches for OFDMA multi-user multi-cellular networks

The paper studies two resource allocation strategies (GRID, anti-EMI) for multi-user OFDMA systems. These strategies are evaluated after being compared with the Round Robin and the FFR strategy in terms of mean throughput and mean dissipated power. All investigated strategies assign resources without Channel State Information (CSI), while both GRID and anti-EMI inherently combat Co-Channel Interference (CCI); hence they enhance mean throughput. Simulations indicate that GRID outperforms Round Robin and FFR in all scenarios into consideration and competes the anti-EMI strategy in various network orientations. The latter is justified especially for highly populated scenarios (i.e. 50% probability failure and 2 subcarriers per MT). As for the FFR strategy, simulations verify that the spectral efficiency is not the optimum, which fact has been already verified in the respective literature as well. Finally, the platform can inherently spare around the 70% of the maximum available power.

Resource exploitation in multi-carrier multi-cellular networks

The purpose of this paper is to examine the algorithmic quality of a semi-Random subcarrier allocation strategy and a Block Anti-Jamming Subcarrier Scavenging (BAJSS) strategy in terms of mean capacity, mean Bit Error Rate (BER), complexity as well as Jains fairness index (power, capacity). These strategies are implemented in a LTE OFDMA multicellular network platform, which executes a fixed, sufficient for convergence, Monte Carlo (MC) runs. Both strategies are based on anti-jamming criteria so as to further mitigate Intra-Channel Interference (ICI). According to the results, semiRandom outperforms BAJSS and the traditional random strategy in terms of mean capacity, mean BER and power dissipation at the cost however of increased computational complexity.

Interference reduction in MIMO-OFDMA cellular networks via cooperative antenna selection

In this paper, the performance of a proposed antenna selection algorithm is evaluated that is based on cooperative interference mitigation among neighbouring base stations. This algorithm has been evaluated in MIMO - OFDMA multicellular networks, for various bit rates per mobile user and blocking probabilities via extended Monte Carlo simulations. As results indicate, for 64QAM modulation type and 3/4/5 allocated subcarriers per mobile user, the proposed antenna selection approach can provide up to 50%/36%/25% gain on the mean number of active users in the network compared to the case where antenna selection is performed having as sole criterion the maximization of Signal to Noise Ratio.