Sa’ad Petrous Mansoor

Wavelength reused bidirectional transmission of adaptively modulated optical OFDM signals in WDM-PONs incorporating SOA and RSOA intensity modulators.

Detailed numerical investigations are undertaken of wavelength reused bidirectional transmission of adaptively modulated optical OFDM (AMOOFDM) signals over a single SMF in a colorless WDM-PON incorporating a semiconductor optical amplifier (SOA) intensity modulator and a reflective SOA (RSOA) intensity modulator in the optical line termination and optical network unit, respectively. A comprehensive theoretical model describing the performance of such network scenarios is, for the first time, developed, taking into account dynamic optical characteristics of SOA and RSOA intensity modulators as well as the effects of Rayleigh backscattering (RB) and residual downstream signal-induced crosstalk. The developed model is rigorously verified experimentally in RSOA-based real-time end-to-end OOFDM systems at 7.5 Gb/s. It is shown that the RB noise and crosstalk effects are dominant factors limiting the maximum achievable downstream and upstream transmission performance. Under optimum SOA and RSOA operating conditions as well as practical downstream and upstream optical launch powers, 10 Gb/s downstream and 6 Gb/s upstream over 40 km SMF transmissions of conventional double sideband AMOOFDM signals are feasible without utilizing in-line optical amplification and chromatic dispersion compensation. In particular, the aforementioned transmission performance can be improved to 23 Gb/s downstream and 8 Gb/s upstream over 40 km SMFs when single sideband subcarrier modulation is adopted in the downstream systems.

Reproducing oscillatory behaviour of a hydroelectric power station by computer simulation

Abstract This paper describes a complex simulation of a pumped-storage hydroelectric power station. Dinorwig power stations fast response is essential for controlling the electricity supply frequency on the national grid in Great Britain. The paper describes the stations key physical features and it is shown that the plant is nonlinear, multivariable and time-varying. The details of a Simulink® model, which is valid over a wide range of operating conditions, are presented. The improved understanding of the stations dynamic characteristics is illustrated by using the simulation to investigate an incident of oscillatory behaviour in its power output.

Predictive feedforward control for a hydroelectric plant

In this brief, it is shown that predictive feedforward control can be used to help a hydroelectric plant achieve its target for delivered power while operating in grid (power system) frequency control mode. Due to the fundamental limitation on how fast the water in the supply tunnel can be accelerated by gravity, a hydraulic turbine is always subject to some delay between opening or closing its guide vane and the consequent change in power. Here, it is proposed that the effect of this delay can be alleviated by predicting 3-4 s ahead what power will be required, based on grid frequency measurements, and using this as a feedforward signal to supplement the normal PID feedback controller. Results are presented to show the improved accuracy of power delivery achieved with this approach.

Adaptively modulated optical OFDM modems utilizing RSOAs as intensity modulators in IMDD SMF transmission systems

Detailed investigations of the transmission performance of adaptively modulated optical orthogonal frequency division multiplexed (AMOOFDM) signals converted using reflective semiconductor optical amplifiers (RSOAs) are undertaken over intensity-modulation and direct-detection (IMDD) single-mode fiber (SMF) transmission systems for WDM-PONs. The theoretical RSOA model adopted for modulating the AMOOFDM signals is experimentally verified rigorously in the aforementioned transmission systems incorporating recently developed real-time end-to-end OOFDM transceivers. Extensive performance comparisons are also made between RSOA and SOA intensity modulators. Optimum RSOA operating conditions are identified, which are independent of RSOA rear-facet reflectivity and very similar to those corresponding to SOAs. Under the identified optimum operating conditions, the RSOA and SOA intensity modulators support the identical AMOOFDM transmission performance of 30Gb/s over 60km SMFs. Under low-cost optical component-enabled practical operating conditions, RSOA intensity modulators with rear-facet reflectivity values of >0.3 outperform considerably SOA intensity modulators in transmission performance, which decreases significantly with reducing RSOA rear-facet reflectivity and optical input power. In addition, results also show that use can be made of the RSOA/SOA intensity modulation-induced negative frequency chirp to improve the AMOOFDM transmission performance in IMDD SMF systems.

Real-time experimental demonstrations of software reconfigurable optical OFDM transceivers utilizing DSP-based digital orthogonal filters for SDN PONs.

Real-time optical OFDM (OOFDM) transceivers with on-line software-controllable channel reconfigurability and transmission performance adaptability are experimentally demonstrated, for the first time, utilizing Hilbert-pair-based 32-tap digital orthogonal filters implemented in FPGAs. By making use of an 8-bit DAC/ADC operating at 2GS/s, an oversampling factor of 2 and an EML intensity modulator, the demonstrated RF conversion-free transceiver supports end-to-end real-time simultaneous adaptive transmissions, within a 1GHz signal spectrum region, of a 2.03Gb/s in-phase OOFDM channel and a 1.41Gb/s quadrature-phase OOFDM channel over a 25km SSMF IMDD system. In addition, detailed experimental explorations are also undertaken of key physical mechanisms limiting the maximum achievable transmission performance, impacts of transceivers channel multiplexing/demultiplexing operations on the system BER performance, and the feasibility of utilizing adaptive modulation to combat impairments associated with low-complexity digital filter designs. Furthermore, experimental results indicate that the transceiver incorporating a fixed digital orthogonal filter DSP architecture can be made transparent to various signal modulation formats up to 64-QAM.

Performance analysis of stream and block cipher algorithms

Cryptographic algorithms play a big role in providing data security against malicious attacks. However, they are computationally intensive applications and consume large amount of CPU time. In mobile devices network security is very important, and different type of cryptographic algorithm is used to prevent malisons attack on the transmitted data. This work provides comparison between block and stream cipher algorithms, using different data sizes and key sizes. It provides evaluation between 12 commonly used algorithms. Based on our simulation results it can be seen that stream cipher algorithm in general perform better than block cipher algorithm with regards to CPU time required for encryption.

A standard method for specifying the response of hydroelectric plant in frequency-control mode

Abstract The paper proposes a specification for the transient and steady-state responses of a hydroelectric power station operating in frequency-control mode. It can be used during design, testing and commissioning as well as forming the basis for contractual agreement on performance during normal operation. The specification gives a generic definition of how the electrical power should respond to step, ramp and random changes in frequency. The rationale for the proposed specification is discussed. A prototype transfer function is proposed as an aid to formulating a step response specification. The length of record required during random testing is discussed. The use of the specification is illustrated by considering the response of the Dinorwig pumped-storage hydroelectric station.

Using a fuzzy inference system to control a pumped storage hydro plant

The paper discusses the development of a fuzzy inference system (FIS) based governor control for a pumped storage hydroelectric plant. The First Hydro Companys plant at Dinorwig in North Wales is the largest of its kind in Europe and is mainly used for frequency control of the UK electrical grid. In previous investigations, a detailed model of the plant was developed using MATLAB/sup (R)//SIMULINK/sup (R)/ and this is now being used to compare FIS governor operation with the proportional-integral-derivative (PID) controller currently used. The paper describes the development of an FIS governor, and shows that its response to a step increase in load is superior to the PID under certain conditions of load. The paper proceeds to discuss the implications of these results in view of the possible practical application of an FIS governor at the Dinorwig plant.

Stability of a pump storage hydro-power station connected to a power system

The operational flexibility of pumped storage hydropower stations means that they are often used for the control of power system frequency. When used in this role, the response of the power station is determined by the behaviour of its governor, the stiffness of the connected grid and the interaction between the governor and the grid. An investigation into the governor settings at Dinorwig power station in the UK has been undertaken in order to establish the optimum governor settings for different loading conditions, providing as close to an ideal response as possible without endangering the stability of system frequency control. The gain and phase margins of the open loop transfer function of the system were examined to determine the stability of the power system, and the effect of the droop settings and the grid size are included in the study. Information on stability of the power station is presented for a variety of operating and grid conditions.

Multi-modal biometric emotion recognition using classifier ensembles

We introduce a system called AMBER (Advanced Multimodal Biometric Emotion Recognition), which combines Electroencephalography (EEG) with Electro Dermal Activity (EDA) and pulse sensors to provide low cost, portable real-time emotion recognition. A single-subject pilot experiment was carried out to evaluate the ability of the system to distinguish between positive and negative states of mind provoked by audio stimuli. Eight single classifiers and six ensemble classifiers were compared using Weka. All ensemble classifiers outperformed the single classifiers, with Bagging, Rotation Forest and Random Subspace showing the highest overall accuracy.