Muhammad Junaid Mughal

Performance Comparison of DFT, Discrete Wavelet Packet and Wavelet Transforms, in an OFDM Transceiver for Multipath Fading Channel

Multi-carrier modulation (MCM) schemes divide the broadband frequency-selective channel into parallel, flat-fading subchannels of equal bandwidth and interspacing. A cyclic prefix is appended to each symbol, in order to mitigate inter-symbol interference (ISI), however it leads to spectral inefficiency. Moreover, OFDM transceivers suffer from poor frequency characteristics. Perfect reconstruction wavelet packet transmultiplexer in an OFDM transceiver counters the degrading effects of ISI, and also conserves bandwidth. In this paper we give the performance comparison of conventional discrete Fourier transform (DFT) with discrete wavelet packet transform (DWPT) in an OFDM transceiver. Two of the most popular wavelets, namely Haar and Daubechies wavelets are used for DWPT in a multipath flat-fading and frequency selective-fading channel. A comparison between wavelets and wavelet packets is also given and it is shown that wavelet packets outperform wavelets

THE WAVE EQUATION AND GENERAL PLANE WAVE SOLUTIONS IN FRACTIONAL SPACE

This work presents the analytical solution of vector wave equation in fractional space. General plane wave solution to the wave equation for flelds in source-free and lossless media is obtained in fractional space. The obtained solution is a generalization of wave equation from integer dimensional space to a non-integer dimensional space. The classical results are recovered when integer-dimensional space is considered.

AN EXACT SOLUTION OF THE CYLINDRICAL WAVE EQUATION FOR ELECTROMAGNETIC FIELD IN FRACTIONAL DIMENSIONAL SPACE

This work deals with an exact solution of cylindrical wave equation for electromagnetic fleld in fractional dimensional space. The obtained fractional solution is a generalization of the cylindrical wave equation from integer dimensional space to a fractional dimensional space. The resulting theoretical framework can be used to study the phenomenon of electromagnetic wave propagation in any fractal media because fractal media can be described as an ordinary media in a fractional dimensional space. The classical results are recovered from fractional solution when integer dimensional space is considered.

Differential Electromagnetic Equations in Fractional Space

In this chapter a novel generalization of differential electromagnetic equations in fractional space is provided. Firstly, basic vector differential operators are generalized in fractional space and then using these fractional operators Maxwell’s, Laplace’s, Poisson’s and Helmholtz’s equations have been worked out in fractional space. The differential electromagnetic equations in fractional space, established in this chapter, provide a basis for application of the concept of fractional space in practical electromagnetic wave propagation and scattering problems in fractal media.

On electromagnetic wave propagation in fractional space

The wave equation has very important role in many areas of physics. It has a fundamental meaning in classical as well as quantum field theory. With this view, one is strongly motivated to discuss solutions of the wave equation in all possible situations. The wave equation in fractional space can effectively describe the wave propagation phenomenon in fractal media. In this chapter, exact solutions of different forms of wave equation in \(D\)-dimensional fractional space are provided, which describe the phenomenon of electromagnetic wave propagation in fractional space.

Paraboloidal Reflector in Chiral Medium Supporting Simultaneously Positive Phase Velocity and Negative Phase Velocity

A ski bar hold down assembly including a post is rotatably and slideably mounted to a ski bar for use in mounting the ski bar to a trailer. The assembly includes a stop on a lower end of the post engaged with a lower surface of the trailer. The assembly further includes a releasable clamp mounted to an upper end of the post and engaged with a top of the ski bar. The clamp selectively mounts the ski bar to the trailer so as to mount snowmobile skis of a snowmobile between the ski bar and the trailer. If desired, the hold down assembly can also be mounted to the trailer even if no snowmobile is present. A method of mounting the ski bar is provided including the steps of inserting a post of a hold down assembly into a passage in the platform of the trailer, rotating the post 90 DEG , then moving a clamp on the assembly to clamp the ski bar to the trailer.

AN EXACT SOLUTION OF THE SPHERICAL WAVE EQUATION IN D-DIMENSIONAL FRACTIONAL SPACE

In this paper, an exact solution of the spherical wave equation is obtained in D-dimensional fractional space. The obtained fractional space solution provides a generalization of electromagnetic wave propagation phenomenon from integer space to the fractional space. The classical results are recovered from fractional space solution, when integer space is considered. The investigated solution is useful for studying the electromagnetic wave propagation phenomenon in spherical geometries consisting fractal media.

Reflection and Transmission at Dielectric-Fractal Interface

The transmission and reflection of electromagnetic waves at dielectric-fractal interface is studied, the fractal exhibits quasi fractional space properties. The closed form expressions for transmission and reflection coefficients are formulated for such an interface. The classical results are obtained when integer dimensions, instead of fractional dimension are inserted in the said expressions. This work can be used to study behavior of electromagnetic waves in slabs and waveguides filled with fractal media.

Performance Comparison of DFT-OFDM and Wavelet-OFDM with Zero-Forcing Equalizer for FIR Channel Equalization

In conventional DFT based orthogonal frequency division multiplexing (OFDM), cyclic prefix (CP) is used to avoid the inter symbol interference (ISI) caused by a time dispersive channel. A solution has been proposed in literature, which involves replacing DFT with wavelet packet transform (WPT) in communication systems. WPT does not require CP and has the attraction of having much lower side lobes. However, in wavelet based multicarrier systems, channel equalization remains an open research area. In this article, a time-domain zero-forcing equalizer (ZFE) for wavelet packet based OFDM (WOFDM) is proposed. The performance comparison of DFT-OFDM and WOFDM is given for an arbitrary FIR channel with different types of wavelet packets. Simulation results show improvement in bit error rate (BER) performance for WOFDM.

Compact acoustooptic high-speed variable attenuator for high-power applications

For the first time, a >65-dB dynamic range fast 2.8 /spl mu/s fiber-optic variable optical attenuator is proposed and demonstrated by using a single bulk acoustooptic device. The unique double-pass optical design eliminates intrinsic acoustooptic interaction-based Doppler shift, while a center path positioned halfwave plate greatly reduces polarization dependent loss to 0.03 dB. The current attenuators insertion loss is <2.5 dB with a demonstrated 1520-1600 nm operation. Due to its bulk crystal nature, this attenuator can handle high power optical beams.