Mehmet Toycan

Bi-directional, 480Mbps, ultra-wideband, radio-over-fibre transmission using a 1310/1564nm reflective electro-absorption transducer and commercially-available components

We present the first experimental demonstration of a bi-directional, reflective, electro-absorption transducer-based, 480 Mbps UWB-wireless/optical transmission system. A -21.4 dB error vector magnitude was observed over 1 km of single mode fibre.

Graeco-Latin-routed, self-wrapping, FSR-interleaved, AWG-based access network

Feature Issue on Passive Optical Network Architectures and TechnologiesWe describe, to the best of our knowledge, a novel WDM-TDM switched access network architecture featuring cascaded 16×16 and 1×32 arrayed waveguide gratings (AWGs), such that the AWG free spectral ranges (FSRs) have been matched to provide cascaded, cyclical, Graeco-Latin-routing protocols for downstream and upstream routing. In particular, use of FSR-multiplexed wavelengths allows greatly reduced cross talk between upstream and downstream signals and also doubling of the available network bandwidth capacity, while maintaining the same N×N AWG in the central office. Alternatively, this allows significant increase in the number of end users served by the network. We provide theoretical and simulation studies of our bidirectional access network topology, and experimental proof of principal results. Three sets of simulations with data rates from 2.5, 5.0, and 10.0Gbits/s have been performed for downstream and upstream transmissions. For the experimental part, eight ITU wavelengths were multiplexed at the exchange point and successfully transmitted at 2.5Gbits/s for simultaneous bidirectional transmission. Bit-error-rate measurements show error-free transmission is achievable for both directions with minimal cross talk between the channels.

Cost and energy efficient operation of converged, reconfigurable optical wireless networks

This paper presents a converged fibre-to-the-home (FTTH) based access network architecture featuring wireless services. In order to fulfill the bandwidth demands from end users, a dynamic architecture is proposed with co-existence of LTE, WiMax and UWB technologies. Hybrid wavelength division multiplexing (WDM) and a time division multiplexing (TDM) based optical access network offer reconfigurable provision. This enhances the ability to allocate different wavelengths to different optical networking units (ONUs) on demand. In addition, two different channel routing modules (CRMs) are introduced in order to address the cost effectiveness and energy efficiency issues of the proposed network. Take-up rate adaptive-mode operation and traffic-adaptive power management are utilized to optimize the benefits of low investment cost with energy efficiency. Up to 26% power consumption reduction is achieved at the time of minimum traffic conditions while 10% consumption is achieved at the time of maximum traffic conditions. Besides, 23% energy saving can be achieved compared to conventional systems in fully operated stage.

Modified Hilbert fractal geometry, multi‐service, miniaturized patch antenna for UWB wireless communication

Purpose – The purpose of this paper is to describe a modified Hilbert‐based fractal antenna for ultra wideband (UWB) wireless applications. Simulation results show excellent multi‐band characteristics for UWB wireless applications.Design/methodology/approach – A Hilbert curve‐based fractal is optimised for self‐replicating, space‐filling and self‐avoiding properties. In the proposed design, the Hilbert curve is applied to a rectangle as an initial iteration and maintained for the later iterations. Additionally, a Yagi‐like strip is removed from the second iteration of the Hilbert patch and a hexagonal portion is removed from the substrate to achieve good optimization. The antenna feed is created through a micro‐strip line with a feeding section. Finally, a partial ground plane technique is used for improved impedance matching characteristics. A finite element method (FEM) is used to simulate the modified Hilbert model with commercially available Ansoft HFSS software.Findings – The proposed antenna is mini...

A fractal geometry, multi-band, miniaturized monopole antenna design for UWB wireless applications

A new combined fractal geometry based Monopole antenna design for ultra wideband (UWB) applications is presented in this paper. This fractal structure is implemented on square and Minkowski fractal is applied to the lines of a square. Then, a Sierpinski carpet fractal is formed on the first iteration of the Minkowski fractal. The proposed antenna is miniaturized (45 mm × 45 mm) and has multi-band characteristics. Simulation results show that the presented antenna has a reflection coefficient characteristic < −15dB, 80% radiation efficiency, 4–6dBi antenna gain and omni-directional radiation pattern properties over the UWB bandwidth (3.1 – 10.6 GHz). The gain variation is due to increased directivity at higher frequencies.

Study of Hybrid Cascaded AWG-based Access Network Topology

We describe an upgrade scenario from current passive optical networks (PON) to wavelength routed fibre-to-the-home (FTTH) networks. The theoretical and experimental study of a bidirectional access network topology based on cascaded arrayed waveguide gratings (AWG) is presented. By combining a 16times16 AWG in the exchange point and multiple 1times16 AWGs in the distribution points, N2 users can be addressed when N wavelengths are transmitted. 16 ITU wavelengths have been multiplexed at the exchange point and successfully transmitted at 2.5 Gb/s data rates for simultaneous bidirectional transmission. Bit error rate measurements have shown error free transmission is achievable for both directions and minimal crosstalk between the channels can be noticed in the retrieved eye diagrams

Machine-based classification of ADHD and nonADHD participants using time/frequency features of event-related neuroelectric activity

OBJECTIVE Attention-deficit/hyperactivity disorder (ADHD) is the most frequent diagnosis among children who are referred to psychiatry departments. Although ADHD was discovered at the beginning of the 20th century, its diagnosis is still confronted with many problems. METHOD A novel classification approach that discriminates ADHD and nonADHD groups over the time-frequency domain features of event-related potential (ERP) recordings that are taken during Stroop task is presented. Time-Frequency Hermite-Atomizer (TFHA) technique is used for the extraction of high resolution time-frequency domain features that are highly localized in time-frequency domain. Based on an extensive investigation, Support Vector Machine-Recursive Feature Elimination (SVM-RFE) was used to obtain the best discriminating features. RESULTS When the best three features were used, the classification accuracy for the training dataset reached 98%, and the use of five features further improved the accuracy to 99.5%. The accuracy was 100% for the testing dataset. Based on extensive experiments, the delta band emerged as the most contributing frequency band and statistical parameters emerged as the most contributing feature group. CONCLUSION The classification performance of this study suggests that TFHA can be employed as an auxiliary component of the diagnostic and prognostic procedures for ADHD. SIGNIFICANCE The features obtained in this study can potentially contribute to the neuroelectrical understanding and clinical diagnosis of ADHD.

Dual band implant antenna design with miniaturized and biocompatible characteristics for wireless health monitoring

In this paper, the combination of Hilbert fractal geometry and the serpentine shape based microstrip implant antenna design proposed and optimized for wireless medical applications. The proposed antenna is miniaturized 5.5 × 5.8 × 1.7 (width × height × thickness mm3) and operates for dual band (MICS 402-405 MHz ile ISM 2.4-2.48GHz) operations. Superstrate is applied on top of the antenna to avoid a direct contact with the metallization and achieve biocompatibility. Implant antenna is simulated in three layer tissue (skin, fat and muscle) model. Simulation results show that the presented antenna has a reflection coefficient characteristic better than -10dB, omni-directional radiation pattern and acceptable specific absorption rate values for human body.

Investigation of chromatic dispersion effect on 802.16 WiMax over long haul transmission distances

We present a novel FTTH based access network architecture that integrates the wireless and wired services in a converged provision with dynamic bandwidth allocation. A wide range of interactive multimedia services are available to end-users by using latest-generation, OFDM based wireless technologies. Direct VCSEL modulation with 16QAM and 64QAM OFDM based WiMax signal (3.5 GHz) was modeled by using VPItransmissionMaker for upstream transmission by investigating the error vector magnitudes (EVMs). WiMax over standard single mode fibre (SSMF) is first examined and maximum limit stated in current standard of IEEE 802.16 WiMAX using 16QAM (EVM of -24.43 dB) and 64QAM (EVM of -30.4 dB) are achieved at 110km and 95 km respectively. For the second part of the analysis, dispersion compensating fiber (DCF) is deployed in order to achieve long haul transmission distances. A maximum achievable distance of 600km and 450km was realized with -27.6 dB EVM results after dispersion compensation technique applied to both 16QAM and 64QAM OFDM based WiMax respectively.

Design of a low-loss and multi-band fractal-based antenna for ultra wide band communication

As the demand for high bandwidth applications is increasing for wireless communication, the need for wideband antennas increases as well. In this paper, a new small fractal antenna design concept is proposed for ultra wideband (UWB) applications. UWB is a technology that high data rates (480Mb/s) and high bandwidth (0.528 – 7.5 GHz) with good signalling characteristics for wireless personal area networks (WPAN). First band group (BG:1, 3.1 – 4.752 GHz) of the UWB band is simulated and −41.3 dBm/MHz is observed. Fractal antenna geometry shows self-similarity characteristics that operates at multiple wavelengths with similar radiation patterns. Therefore, it is suitable to use for multi band orthagonal frequency division multiplexing (MB-OFDM) based UWB applications. Proposed fractal antenna design is analysed with less than −20dB return loss (S11) over whole UWB bandwidth (3.1 – 10.6 GHz). In addition to this, omni directional radiation pattern is observed for the BG:1 of the UWB band.