Georgia D. Ntouni

Reliable and Energy-Efficient Communications for Wireless Biomedical Implant Systems

Implant devices are used to measure biological parameters and transmit their results to remote off-body devices. As implants are characterized by strict requirements on size, reliability, and power consumption, applying the concept of cooperative communications to wireless body area networks offers several benefits. In this paper, we aim to minimize the power consumption of the implant device by utilizing on-body wearable devices, while providing the necessary reliability in terms of outage probability and bit error rate. Taking into account realistic power considerations and wireless propagation environments based on the IEEE P802.l5 channel model, an exact theoretical analysis is conducted for evaluating several communication scenarios with respect to the position of the wearable device and the motion of the human body. The derived closed-form expressions are employed toward minimizing the required transmission power, subject to a minimum quality-of-service requirement. In this way, the complexity and power consumption are transferred from the implant device to the on-body relay, which is an efficient approach since they can be easily replaced, in contrast to the in-body implants.

Throughput Maximization in Multicarrier Wireless Powered Relaying Networks

Dynamic power allocation and power splitting, in a multicarrier two-hop link with a wireless powered relay, is investigated. We first formulate the corresponding optimization problem, which consists of the joint optimization -in terms of achievable rate- of, 1) the dynamic power allocation among multiple channels and, 2) the selection of the power splitting ratio between information processing and energy harvesting at the relay, when amplify-and-forward is applied. This is a non-convex optimization problem, which is mapped to a convex one and optimally solved using one-dimensional search and dual decomposition, while a suboptimal efficient iterative method is also proposed. Simulations reveal a significant increase in the throughput, when comparing the proposed approach with two alternative power allocation schemes, while they verify the effectiveness of the fast-converging iterative solution.

OFDM-IM vs FQAM: A comparative analysis

Recently, orthogonal frequency division multiplexing (OFDM) with index modulation (OFDM-IM) as well as frequency and quadrature amplitude modulation (FQAM) have been proven to be promising techniques for the multicarrier transmission over frequency selective fading channels by successfully mitigating the induced interference due to multipath, while at the same time boosting the overall spectral efficiency. In this paper, we present a thorough study of OFDM-IM and FQAM schemes and conduct a comparison between them and the classic OFDM system. Different configurations are considered and evaluated in terms of their spectral efficiency and error performance, capitalizing on recent results from the literature.

On the Optimal Tone Spacing for Interference Mitigation in OFDM-IM Systems

Orthogonal frequency division multiplexing with index modulation (OFDM-IM) has been recently proposed as an efficient technique to improve the error performance and enhance the spectral efficiency achieved by the classical OFDM. In this letter, we minimize the presence of intercarrier and intersymbol interference, experienced by OFDM-IM systems under mobility conditions and multipath scenarios, by selecting the appropriate tone spacing between adjacent subcarriers. Finally, we prove that the optimal value of tone spacing increases the system capacity, occupying only the necessary amount of bandwidth, and provide closed-form expressions for the interference power per active subcarrier.

Inter-band carrier aggregation in heterogeneous networks: Design and assessment

This paper deals with the performance assessment of the Long Term Evolution (LTE)-Advanced Release 12 physical downlink channel, emphasizing on the Carrier Aggregation (CA) technology and its recent advances, such as the challenging interband non-contiguous solution. By processing the LTE-Advanced waveforms in the time domain (instead of the more common baseband), we describe the underlying system model and the associated simulation setup in detail. The error performance of the system is evaluated under different physical layer parameters and CA scenarios, according to the latest updates of the Third Generation Partnership Project (3GPP) technical specifications. Our analysis reveals that the Heterogeneous Band (HetBand) non-contiguous CA technology can be efficiently applied to the design of next generation mobile broadband networks, given that the exploitation of both unlicensed and frequency dispersed bands might be a promising solution against the spectrum scarcity.

Error performance of power line communications in the presence of Nakagami-m background noise

Funding information Alexander Onassis Foundation Abstract This paper studies the error performance of power line communication (PLC) systems, in the presence of background noise with Nakagami-m distributed envelope and uniformly distributed phase. In this sense, we present closed-form expressions for the symbol error rate (SER) of PLC systems using binary pulse amplitude modulation and generalize the analysis to accommodate the M-ary pulse amplitude modulation. In addition, novel closed-form expressions for the SER upper bound of rectangular quadrature amplitude modulation PLC systems are derived. Interestingly, these expressions can be considered as tight SER approximations in the high–signal-to-noise ratio region and, thus, can efficiently evaluate the operational bound of a PLC system.

On the optimal timing of detection in molecular communication systems

In this paper, the error performance of a molecular communication via diffusion system in the absence of flow is analysed. Closed-form expressions for the bit error rate are presented and utilized to enhance the timing of the receivers observations, which are used in the detection of the transmitted information. More precisely, we specify the optimal time, when the observation process should start and finish, in order to achieve the minimum probability of error. Furthermore, in the case where the receiver counts the molecules at specific time instants, an advantageous sampling time has been proposed, along with the ideal number of samples that should be collected in order to minimize the error probability. Finally, closed-form expressions for the first sample and the total number of samples that should be considered, have been derived and validated through extensive simulations.

Comparison of amplitude detection techniques for passive receivers in molecular communications

Amplitude detection is based on observations of the information carrying molecules made at the receiver and can be enhanced by optimizing the timing and the number of them. In this paper, a diffusion-based molecular communications system with a passive receiver is analysed under two different amplitude based detection techniques. In particular, low complexity detectors utilizing a single or multiple observations are evaluated and compared in terms of the achievable mean error probability, when external noise and interference are considered.

A Low-Complexity Detector for BPPM Systems Under Additive Gaussian Mixture Noise

We analyze the performance of the single-threshold detector (STD) for binary pulse position modulation in the presence of symmetric Gaussian mixture noise (GMN). We first derive a general closed-form expression for the average error probability that is later used to investigate the optimality of the STD with zero threshold, which is the simplest form of STD. We also establish conditions sufficient to guarantee minimum error rates with the low-complexity STD for a wide range of signal-to-noise ratio. The theoretical results are verified through simulations of GMN with various noise parameters.