Low-cost Cognitive Radios against Spectrum Scarcity

The next generation wireless networks are envisioned to deal with the expected thousand-fold increase in total mobile broadband data and the hundred-fold increase in connected devices. In order to provide higher data rates, improved end-to-end performance, low latency, and low energy consumption at a low cost per transmission, the fifth generation (5G) systems are required to overcome various handicaps of current cellular networks and wireless links. One of the key handicaps of 5G systems is the performance degradation of the communication link, due to the use of low-cost transceiver in high data rate. Motivated by this in this paper, we discuss the impact of transceiver front-end hardware imperfections on the spectrum sensing performance of cognitive radios.Comment: 4 pages, 4 figure

Ergodic capacity evaluation of wireless THz fiber extenders

This paper focuses on delivering quantified results for the evaluation of the aggregated impact of stochastic antenna misalignment, multipath fading and hardware imperfections on the terahertz (THz) wireless fiber extenders. In this line, we present the appropriate signal model that accommodates the different technical and environmental parameters. In particular, it takes into consideration the antenna gains, the central frequency, the transmission range, the environmental conditions, i.e. temperature, humidity and pressure, the spatial jitter between the transmitter and receiver antennas, which results to antenna misalignment, the intensity of hardware imperfections, and the stochastic behavior of the wireless channel. Based on this model, we assess the joint impact of antenna misalignment and multipath fading, by providing Monte Carlo simulation results for the channels ergodic capacity.Comment: 4 pages, 2 figures, conference paper, Presented in WWRF, WG High Frequencies (mmWAVE and THz) Radio Communications Technologies, September 201

Relay-Based Blockage and Antenna Misalignment Mitigation in THz Wireless Communications

The proliferation of wireless devices in recent years has caused a spectrum shortage, which led the scientific community to explore the potential of using terahertz (THz) communications. However, THz systems suffer from severe path attenuation, blockage, and antenna misalignment. In this paper, we present a relay-based blockage and antenna misalignment mitigation approach. In more detail, two relay selection policies are employed, namely best and random relay selection. The system performance under both policies is evaluated and compared in terms of average throughput and the probability that throughput of a link is below the quality of service (QoS) threshold, using Monte Carlo simulations. It was observed that the effect of both blockage and misalignment can be mitigated using relays. Moreover, the gain of using relaying to mitigate blockage is much more significant.Comment: 4 page, 4 figures, 6G summi

Ergodic capacity analysis of reconfigurable intelligent surface assisted wireless systems

This paper presents the analytic framework for evaluating the ergodic capacity (EC) of the reconfigurable intelligent surface (RIS) assisted systems. Moreover, high-signal-to-noise-ratio and high-number of reflection units (RUs) approximations for the EC are provided. Finally, the special case in which the RIS is equipped with a single RU is investigated. Our analysis is verified through respective Monte Carlo simulations, which highlight the accuracy of the proposed framework.Comment: 6 pages, 3 figures, accepted in IEEE 5G world foru

Performance Evaluation of Reconfigurable Intelligent Surface Assisted D-band Wireless Communication

In the recent years, the proliferation of wireless data traffic has led the scientific community to explore the use of higher unallocated frequency bands, such as the millimeter wave and terahertz (0.1-10 THz) bands. However, they are prone to blockages from obstacles laid in the transceiver path. To address this, in this work, the use of a reconfigurable-intelligent-surface (RIS) to restore the link between a transmitter (TX) and a receiver (RX), operating in the D-band (110-170 GHz) is investigated. The system performance is evaluated in terms of pathgain and capacity considering the RIS design parameters, the TX/RX-RIS distance and the elevation angles from the center of the RIS to the transceivers.Comment: 6 pages, 5 figures, accepted for presentation in IEEE 5G World Forum 202

Analytical Performance Evaluation of Beamforming Under Transceivers Hardware Imperfections

In this paper, we provide the mathematical framework to evaluate and quantify the performance of wireless systems, which employ beamforming, in the presence of hardware imperfections at both the basestation and the user equipment. In more detail, by taking a macroscopic view of the joint impact of hardware imperfections, we introduce a general model that accounts for transceiver impairments in beamforming transmissions. In order to evaluate their impact, we present novel closed form expressions for the outage probability and upper bounds for the characterization of the system's capacity. Our analysis reveals that the level of imperfection can significantly constraint the ergodic capacity. Therefore, it is important to take them into account when evaluating and designing beamforming systems.Comment: 7 pages, 5 figures, IEEE WCNC 201

Outage Probability Analysis of THz Relaying Systems

This paper focuses on quantifying the outage performance of terahertz (THz) relaying systems. In this direction, novel closed-form expressions for the outage probability of a dual-hop relaying system, in which both the source-relay and relay-destination links suffer from fading and stochastic beam misalignment, are extracted. Our results reveal the importance of taking into account the impact of beam misalignment when characterizing the outage performance of the system as well as when selecting the transmission frequencies.Comment: 7 pages, 10 figures, conferenc

A cooperative localization-aided tracking algorithm for THz wireless systems

In this paper, a novel cooperation-aided localization and tracking approach, suitable for terahertz (THz) wireless systems is presented. It combines an angle of arrival (AoA) tracking algorithm with the two-way time of arrival method, in order to accurately track the user equipment (UE) position and reduce the deafness caused by the estimation errors of the tracking algorithms. This algorithm can be used by one base station (BS) to estimate the UE position, or by multiple BSs, that cooperate with each other to increase the accuracy of the estimations, as well as the probability of successful estimations and guarantee low-estimation overhead. The efficiency of the algorithm is evaluated in terms of deafness and probability of successful AoA estimation and is compared with the corresponding performance of the fast channel tracking algorithm.Comment: 7 pages, 6 figures, IEEE WCNC 2019 (accepted paper

Wireless Terahertz System Architectures for Networks Beyond 5G

The present white paper focuses on the system requirements of TERRANOVA. Initially details the key use cases for the TERRANOVA technology and presents the description of the network architecture. In more detail, the use cases are classified into two categories, namely backhaul & fronthaul and access and small cell backhaul. The first category refers to fibre extender, point-to-point and redundancy applications, whereas the latter is designed to support backup connection for small and medium-sized enterprises (SMEs), internet of things (IoT) dense environments, data centres, indoor wireless access, ad hoc networks, and last mile access. Then, it provides the networks architecture for the TERRANOVA system as well as the network elements that need to be deployed. The use cases are matched to specific technical scenarios, namely outdoor fixed point-to-point (P2P), outdoor/indoor individual point-to-multipoint (P2MP), and outdoor/indoor "quasi"-omnidirection, and the key performance requirements of each scenario are identified. Likewise, we present the breakthrough novel technology concepts, including the joint design of baseband signal processing for the complete optical and wireless link, the development of broadband and spectrally efficient RF-frontends for frequencies >275 GHz, as well as channel modelling, waveforms, antenna array and multiple-access schemes design, which we are going to use in order to satisfy the presented requirements. Next, an overview of the required new functionalities in both physical (PHY) layer and medium access control (MAC) layers in the TERRANOVA system architecture will be given. Finally, the individual enablers of the TERRANOVA system are combined to develop particular candidate architectures for each of the three technical scenarios.Comment: 73 pages, 31 figures, 7 tables. arXiv admin note: text overlap with arXiv:1503.00697 by other author