The demand for higher broadband speeds is ever increasing whereas the deployment of full fibre to the premises is slower than initially predicted and remains costly. Solutions exploiting the existing, ubiquitous, copper network and increasing its capacity would be highly beneficial in the near term. One approach is to use surface wave (SW) transmission mode to transmit signals over the existing copper cabling network. We present proof-of-concept experimental SW data transmission on twisted pair cables. A surface wave launcher for low GHz carrier frequency operation is designed and optimised. Experimentally, we demonstrate data rates in excess of 12 Gb/s in a 1.15-3.25 GHz band over a 6.1 m twisted pair cable with an average bit error rate of$2.25 \times 10 ^{-5}$, without coding or feedback implementation. Furthermore, higher frequency bands are tested with data rates up to 3.4 Gb/s displaying their potential for surface wave transmission. S-parameter measurements allow capacity estimations of SW data transmission on longer cable lengths using water-filling algorithms. Our calculations predict over 13 Gb/s capacity on a 100 m cable using a 3.5 GHz transmission bandwidth, this may be further extended by further increases to the bandwidth used for SW transmission.

This paper investigates the utilisation of classical antennas as surface wave (SW) launchers. SWs have potential to provide multiplicative factors of increase in the capacity over the existing multi-pair copper wires thanks to their low-loss and extended bandwidth compared to the well-known differential mode signalling, which is operating at sub-GHz frequencies. Although specially designed devices are required for high SW launching efficiencies, classical antennas can be also utilised for launching and receiving SWs by fixing a simple copper wire between antennas. In this way, transmitted power from an antenna is guided along the wire such that the received power of point-to-point wireless communication links can be substantially improved. To prove our claims, we investigate launching and receiving SWs with double-ridged horn antennas from cellular frequencies up to milli-meter wave spectrum. According to the experimental and numerical results, the proposed solution can achieve 30-50dB enhancement in the received power at short to medium communication ranges (under 150m) compared to wireless communication scenarios. Exploiting SWs in the future telecommunication networks may enable substantially improved data rates multi-Gbps links up to Tbps on the last mile without the need of replacing the copper infrastructure with fibre-optic cables. The proposed solution has the potential to provide a cost-effective alternative for enabling high data rate backhaul links required for 6G and beyond communication technologies.

Inspired by nature, molecular communications (MC), i.e., the use of molecules to encode, transmit, and receive information, stands as the most promising communication paradigm to realize the nanonetworks. Even though there has been extensive theoretical research toward nanoscale MC, there are no examples of implemented nanoscale MC networks. The main reason for this lies in the peculiarities of nanoscale physics, challenges in nanoscale fabrication, and highly stochastic nature of the biochemical domain of envisioned nanonetwork applications. This mandates developing novel device architectures and communication methods compatible with MC constraints. To that end, various transmitter and receiver designs for MC have been proposed in the literature together with numerable modulation, coding, and detection techniques. However, these works fall into domains of a very wide spectrum of disciplines, including, but not limited to, information and communication theory, quantum physics, materials science, nanofabrication, physiology, and synthetic biology. Therefore, we believe it is imperative for the progress of the field that an organized exposition of cumulative knowledge on the subject matter can be compiled. Thus, to fill this gap, in this comprehensive survey, we review the existing literature on transmitter and receiver architectures toward realizing MC among nanomaterial-based nanomachines and/or biological entities and provide a complete overview of modulation, coding, and detection techniques employed for MC. Moreover, we identify the most significant shortcomings and challenges in all these research areas and propose potential solutions to overcome some of them.

On-board of aircraft is one of the last venues without high-speed connectivity, which makes it an important problem to address for both industry and academia. To this end, direct air-to-ground communications (DA2GC), where communication link is provided via direct link between aircraft and ground station, is a promising solution to provide high capacity and low latency backhaul capacity for aircraft. In this paper, we investigate the ground station deployment problem to provide 1.2 Gbps average backhaul capacity for each aircraft. The feasible operation points for the key network parameters: the number of ground stations, antenna array size, transmit power and bandwidth, are calculated. In addition, we propose a multi-user beamforming algorithm for dual-polarized hybrid DA2GC antenna arrays, and derive a tractable expression for the DA2GC cell throughput.

Aircraft is one of the last venues with no high-speed connectivity, which makes it an important research issue to address for both industry and academia. This paper introduces seamless gate-to-gate connectivity concept so that passengers can stay connected in all phases of the flight. The backhaul capacity is provided via direct air- to-ground communications links. Passengers can utilize both LTE and Wi-Fi access technologies on-board. In order to avoid interference with licensed ground LTE network, in-cabin LTE users will be served in the unlicensed spectrum via license assisted access (LAA) functionality when the aircraft is close to the ground. In this paper, we determine the altitude threshold for switching to LAA in order to provide seamless LTE connectivity. According to our analysis the myth about the 3 km threshold for the interference with the terrestrial network is not anymore valid. In addition, throughput and user data rates for LTE and Wi-Fi networks are investigated in different flight phases. We have found out that in-cabin LTE network can serve 80-240 users between 5-15 Mbps data rates, and Wi-Fi network can provide peak data rates of 14 Mbps in the worst-case scenario.

Network size and number of mobile users are ever-increasing with the advancements in cellular network technologies. Hence, this situation makes the network monitoring highly complex. Although there are numerous network tomography approaches, service providers need real-time network monitoring tools to provide better network utilization. In this paper, we propose a crowdsourcing-based real-time network tomography framework. In the proposed framework, channel condition and user data usage are monitored via an application at the mobile terminals, and then the mobile terminals transmit their data to the server. In this way, the network and user behavior can be continuously monitored, and real-time actions can be implemented to improve the network performance. By using the proposed framework, we propose an optimization framework for the amount and reporting frequency of the transmitted data to avoid battery drain at the mobile terminal and network congestion. At the end, we provide simulation results for the proposed optimization framework.

As the demand for wireless bandwidth rapidly increases, alternative methods to radio frequency-based communication are investigated to overcome the limited bandwidth problem. Visible light communication (VLC) using light emitting diodes (LEDs) is one of these alternatives. LEDs are estimated to replace the incandescent bulbs within the decade. Since, LEDs can be intensity modulated faster than the human eye can detect, illumination and communication can both be provided by the same lighting system. Indoors communication constitutes 70% of the overall traffic, and VLC is a promising technology to complement Wi-Fi and cellular wireless systems. However, proper handover mechanism should be developed for VLC to be a complete indoors solution. In this paper, we present two soft handover methods for VLC. Simulation results indicate our solutions provide higher data rate for both the overall system and individual users in the handover region.

The capacity gain of MIMO systems significantly depends on the fading correlation between antennas, and there is no analytical study which considers the fading correlation in the troposcatter communications. In this paper, we develop an analytical model, ring scatter model (RSM), to derive the fading correlation in the troposcatter systems as a function of spatial, frequency and angular separations for the first time in the literature. In addition, we compare the effects of the diversity techniques that are suitable for troposcatter communications: space, frequency, angle and space-frequency diversity techniques by deriving the distribution of their achievable data rates with transmit beam-forming. To this end, we extend our previously introduced troposcatter channel model [1] for the implementation of MIMO-OFDM and the diversity techniques.

Troposcatter can be used as a communication medium for beyond-Line-of-Sight (b-LoS) links. However, available troposcatter channel models do not provide comprehensive channel modeling especially at high frequencies. Therefore, the main motivation of this study is to develop a ray-based MIMO troposcatter channel model to analyze transmission-loss characteristics, coherence bandwidth and correlation between antennas for the first time in the literature for troposcatter communications. In addition, the link budget calculations and the distribution of capacity in troposcatter links are provided by using real world water vapor mixing ratio measurements.

Troposcatter communications provide a good alternative for beyond-Line-of-Sight (b-LoS) communication because it can provide reliable high data rate applications with the advancement in the modem and high power amplifiers. The employment of the high data rate applications with troposcatter communications requires the investigation of the troposcatter channels. However, available channel models for the troposcatter communications are not able to take the non-homogeneities of the air turbulence into account. Therefore, the main motivation of this paper is to develop a ray-based MIMO troposcatter channel model in which the beamwidths of the antennas are divided to small parts and, the associated delay and power of the rays are calculated in order to consider the non-homogeneities and time variations of the channel. Also, in order to show the time varying behaviour of the channel this paper provides the simulation results for the maximum data rate of the channel by using real world measurements first time in the literature.

In this paper, we present a dynamic fractional frequency reuse (D-FFR) scheme for OFDMA based cellular networks. The proposed approach is extended from the so-called strict FFR architecture by allowing a fraction of the cell-edge frequencies to be shared by the edge users of the neighboring cells. This sub-band sharing flexibility not only alleviates the spectral deficiency of the strict FFR against soft frequency reuse (SFR) but also improves the already superior performance metrics such as the cell-edge signal-to-noise-plus-interference-ratio (SINR), outage probability and network sum rate throughput. It also provides robustness against sudden and uneven bursts of traffic in one of the cells of the networks. To this end, we provide an analytical framework to determine the coverage probability and the achievable rate of the proposed D-FFR scheme using the parametric models based on stochastic geometry and illustrate the benefits over static (strict or soft) frequency reuse methods via simulation results.