Providing absolute differentiated services for optical burst switching networks: loss differentiation

Kim, S.,Choi, J.S.,Kang, M. IEE 2005 IEE proceedings: Communications Vol.152 No.4

The provision of absolute differentiated services for optical burst switching (OBS) networks based on dynamic wavelength assignment is investigated. Unlike existing quality of service (QoS) schemes, such as buffer-based and offset-time based ones, the proposed dynamic virtual lambda partitioning (DVLP) scheme does not mandate any buffer or extra offset time, but can achieve absolute service differentiation between classes. This new DVLP scheme shares wavelength resources based on several different class priorities in an efficient and QoS guaranteed manner. Furthermore, DVLP is robust: this means that each traffic class, with a loss probability conforming to the target value, continues to receive the required QoS, despite the presence of misbehaving packets, such as bursty arrival traffic. The conditions in which the DVLP scheme is feasible are stated, and the performance results are given for the proposed scheme, which effectively guarantees the target loss probability of each traffic class, both in Poisson and self-similar traffic environments.

Optimisation of remote seeding optical source in wavelength-locked FP-LD bidirectional WDM access optical link

Kwon, H.-C.,Jang, W.-S.,Han, S.-K. IEE 2005 IEE proceedings: Optoelectronics Vol.152 No.5

The optimised characteristics of a wavelength-locked Fabry-Perot laser diode (FP-LD) have been analysed and demonstrated experimentally using remote seeding continuous wave (CW) optical source at central office (CO). The important issues of mode partition noise (MPN) of an FP-LD and Rayleigh backscattering arising from the same wavelength bidirectional transmission are investigated. The Q factor, sidemode suppression ratio (SMSR), and power penalty of a wavelength-locked FP-LD against signal-to-backscattering-power ratio (SBR) were measured. They can be optimised for the SBR range between 22 dB and 31 dB. From the measurements, both the MPN and Rayleigh backscattering can be controlled well owing to remote seeding of an FP-LD and hence use feasibly a wavelength-locked FP-LD in a wavelength division multiplexing-passive optical network (WDM-PON) optical link.

Low-power bus encoding with crosstalk delay elimination

Lyuh, C.-G.,Kim, T. IEE 2006 IEE proceedings: Computers and digital techniques Vol.153 No.2

In deep-submicron technology, minimising the propagation delay and power consumption on buses is the most important design objective in system-on-chip design. In particular, the coupling effects between wires on the bus that can cause serious problems such as crosstalk delay, noise and power consumption. Most of the previous work on bus encoding targeted either (1) minimising the power consumption on bus, (2) minimising the crosstalk delay, or (3) exploiting the known probabilistic information of data, but not all of them. The authors propose a new bus-encoding algorithm that not only minimises the dynamic power consumption on bus but also eliminates the crosstalk delay. The authors achieve the combined objective of (1) and (2) by analysing, formulating and solving the problem of minimising a weighted sum of the self-transition and cross-coupled transition activities on bus in the context of the concept of self-shield encoding. From experiments using a set of benchmark designs, it is shown that the proposed encoding technique consumes 15.4-47.4% less power than existing techniques while totally eliminating the crosstalk delay.

Precision control of single-phase PWM inverter using PLL compensation

Chung, S.K.,Shin, H.B.,Lee, H.W. IEE 2005 IEE proceedings, Electric power applications Vol.152 No.2

High-precision control of a single-phase PWM inverter for constant voltage and constant frequency applications, such as uninterruptible power supplies, is presented. The proposed control employs a capacitor current feedback with a phase-locked loop (PLL) compensator that minimises the steady-state error of the output voltage. The PLL compensator utilises the capacitor voltage and current with a phase difference of 90°. This concept is similar to the dq transform of the three phase variables, and thus the error of the output voltage can be easily minimised by using a proportional-integral type controller. A computer simulation and experiment have been carried out for the actual single-phase PWM inverter controlled by a digital signal processor, and the results clearly demonstrate the effectiveness of the proposed control.

Zero-moment point trajectory modelling of a biped walking robot using an adaptive neuro-fuzzy system

Kim, D.,Seo, S.-J.,Park, G.-T. IEE 2005 IEE proceedings. Control theory and applications Vol.152 No.4

A bipedal architecture is highly suitable for a robot built to work in human environments since such a robot will find avoiding obstacles a relatively easy task. However, the complex dynamics involved in the walking mechanism make the control of such a robot a challenging task. The zero-moment point (ZMP) trajectory in the robot's foot is a significant criterion for the robot's stability during walking. If the ZMP could be measured on-line then it becomes possible to create stable walking conditions for the robot and here also stably control the robot by using the measured ZMP, values. ZMP data is measured in real-time situations using a biped walking robot and this ZMP data is then modelled using an adaptive neuro-fuzzy system (ANFS). Natural walking motions on flat level surfaces and up and down a 10° slope are measured. The modelling performance of the ANFS is optimized by changing the membership functions and the consequent part of the fuzzy rules. The excellent performance demonstrated by the ANFS means that it can not only be used to model robot movements but also to control actual robots.

Fast method to determine an area of vulnerability for stochastic prediction of voltage sags

Park, C.H.,Jang, G. IEE 2005 IEE proceedings: Generation, transmission, and dis Vol.152 No.6

Characterisation of pore structures in nanoporous materials for advanced bionanotechnology

Heo, K.,Yoon, J.,Jin, K.S.,Jin, S.,Ree, M. IEE 2006 IEE proceedings. Nanobiotechnology Vol.153 No.4

Novel reactive-power-compensation scheme for the Jeju-Haenam HVDC system

Jang, G.,Oh, S.,Han, B.M.,Kim, C.K. IEE 2005 IEE proceedings: Generation, transmission, and dis Vol.152 No.4

The paper presents a new reactive-power-compensation scheme for the Jeju-Haenam HVDC system. Owing to changes in the Jeju AC power-system configuration since the Jeju-Haenam HVDC system was constructed, there is an increasing need to modify the existing reactive-power-compensation scheme. In the paper, a new reactive compensation scheme for the stable operation of the HVDC system has been proposed using integer programming to take into account the reactive power supply from new thermal power plants for the Jeju AC power system. An additional objective of the new compensation scheme to minimise the number of components switching in order to reduce temporary overvoltage. Nonlinear time-domain simulations using PSS/E and PSCAD/EMTDC were used to verify the proposed scheme.

Calculation of rightmost eigenvalues in power systems using the block (BACM) Arnoldi Chebyshev method

Lee, B.,Song, H.,Kwon, S.-H.,Kim, D.,Iba, K. IEE 2003 IEE proceedings: Generation, transmission, and dis Vol.150 No.1

Small-signal stability analysis of a power system needs the calculation of the rightmost eigenvalues of a system state matrix. The block Arnoldi Chebyshev method (BACM) is used to calculate the rightmost eigenvalues, which is an improved version of the Arnoldi Chebyshev method (ACM). This method constructs an optimal ellipse containing unwanted eigenvalues and uses the Chebyshev iteration to acquire a restart matrix rich in basis vectors associated with the rightmost eigenvalues. Using the restart matrix including many more basis vectors, this method is good for calculating the clustered rightmost eigenvalues. The proposed algorithm is applied to the IEEE39 New England test system and the results of the experiment are described.

A simple method for acquiring the conducting angle in a multilevel cascaded inverter using step pulse waves

Kang, D.-W.,Kim, H.-C.,Kim, T.-J.,Hyun, D.-S. IEE 2005 IEE proceedings, Electric power applications Vol.152 No.1

In recent years, the multilevel inverter synthesising the output voltage with a step pulse, has been widely used in high power and high voltage applications. To acquire the conducting angles of switches, the conventional method needs to solve simultaneous equations, corresponding to the fundamental and harmonic components, by the use of a Fourier series. Since they are calculated by an iterative method, the process is requires with a large amount of calculation and time. Moreover, they are calculated by means of an off-line operation. To overcome these drawbacks, this paper proposes a simple method of obtaining the conducting angles. This method reduces the amount of calculation needed to obtain the conducting angles and determines them through an on-line operation. It makes use of the voltage-second areas of the divided reference voltage according to the output voltage levels of the inverter. It does not solve the set of nonlinear transcendental equations, but calculates several trigonometric functions. The validity of the proposed method is demonstrated according to each modulation index through simulation and experiment results. The results indicate that the harmonic components obtained by the proposed method are similar to those from the conventional one in the high modulation index. However, in the low modulation index, the proposed method includes more harmonics than the conventional one.