Ergin Dinc

Communicate to illuminate

In the near future, the available radio-frequency (RF) bandwidth will not be sufficient to meet the ever increasing demand for wireless access. Visible light communication (VLC) is an alternative method to reduce the burden of RF-based communication, especially in indoor communications. 70 % of the communication is indoors, and light emitting diode (LED) arrays are spreading for illumination purposes thanks to their low energy and higher lifetime. VLC can be realized as a secondary application in LED arrays that are placed for lighting. In this way, some of the wireless traffic can be sent using light, with less cost and less carbon footprint. For these reasons, VLC attracts significant research interests. We provide an extensive survey of the current literature by outlining challenges and future research areas in order to facilitate future research in this area.

Beyond-line-of-sight communications with ducting layer

Near-surface wave propagation at microwave frequencies, especially 2 GHz and above, shows significant dependence on atmospheric ducts that are the layer in which rapid decrease in the refractive index occurs. The propagating signals in the atmospheric ducts are trapped between the ducting layer and the sea surface, so that the power of the propagating signals do not spread isotropically through the atmosphere. As a result, these signals have low path loss and can travel over the horizon. Since atmospheric ducts are nearly permanent in maritime and coastal environments, ducting layer communication is a promising method for b-LoS communications especially in naval communications. To this end, we overview the characteristics and the channel modeling approaches for ducting layer communications by outlining possible open research areas. In addition, we review the possible utilization of the ducting layer in network-centric operations to empower decision making for the b-LoS operations.

Fading Correlation Analysis in MIMO-OFDM Troposcatter Communications: Space, Frequency, Angle and Space-Frequency Diversity

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.

Soft Handover in OFDMA Based Visible Light Communication Networks

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.

A ray-based channel model for MIMO troposcatter communications

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.

A Ray-Based Channel Modeling Approach for MIMO Troposcatter Beyond-Line-of-Sight (b-LoS) Communications

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.

On dynamic fractional frequency reuse for OFDMA cellular networks

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.

A Nonuniform Spatial Rain Attenuation Model for Troposcatter Communication Links

Troposcatter communication can be used as a communication medium for beyond-line-of-sight (BLOS) links. However, wave propagation in troposphere shows significant dependence on hydro-meteors: especially rain. Therefore, the main motivation of this paper is to develop a rain attenuation model for troposcatter communications, which can model nonuniform multiple rain cells for the first time. At the end, we present simulation results for the amount of rain loss and the distribution of maximum data rates under rain in troposcatter links.

Theoretical Limits on Multiuser Molecular Communication in Internet of Nano-Bio Things

In nano-bio networks, multiple transmitter–receiver pairs will operate in the same medium. Both inter-symbol interference and multi-user interference can cause saturation at the receiver side, and this effect may cause an outage. Thus, we propose a tractable framework to calculate the theoretical operating points for fully absorbing receiver.

In-Flight Broadband Connectivity: Architectures and Business Models for High Capacity Air-to-Ground Communications

In-Flight Broadband Connectivity (IFBC) is a significant open market for mobile network operators, considering that more than 3.3 billion passengers were served by airlines in 2015. On-board broadband services are provided via air-to-ground (A2G) connectivity through direct A2G communication (DA2GC) and satellite A2G communication (SA2GC). Available on-board connectivity systems have significant limitations: high latency in SA2GC and low capacity in DA2GC. The customer expectancy is multi-Mb/s connections in every seat, which leads to capacity requirements of Gb/s to the aircraft. Creation of high capacity IFBC requires a collaborative interaction between different industry partners. For this reason, we investigate A2G architectures in terms of economic and technical perspectives, and propose business models by identifying new roles and positioning them in the A2G business ecosystem. In addition, we provide an extensive summary of the state-of-the-art and future improvements for A2G communications.