An All Digital Implementation of Constant Envelope: Bandwidth Efficient GMSK Modem using Advanced Digital Signal Processing Techniques

Gaussian Minimum Shift Keying (GMSK) has been the most common modulation format belonging to the class of partial response Continuous Phase Modulation (CPM) scheme. It is primarily adopted in the GSM standards (B=0.3) for land mobile radio communication systems because of its high bandwidth efficiency and constant envelope modulation characteristics. The focus of this paper is the design of the demodulator wherein we demonstrate an all digital implementation of sub-optimal synchronization techniques for a GMSK modem based on two Laurent Amplitude modulation pulse (AMP) streams approximation representing the matched filter. In this all digital implementation, we perform a joint estimation of the symbol timing and carrier offset wherein the symbol timing is performed using interpolation techniques.     

An adaptive symbol-spaced equalizer to compensate analog imperfections

This paper presents an adaptive symbol-spaced equalizer solution to compensate for analog imperfections in a single carrier communication systems operating at very high symbol rates up to 500 Msym/s. Pass-band variations in the analog domain are typical at these high data rates, where the required bandwidth is approximately 1 GHz. Non-ideal analog filter responses and phase distortion produce Inter Symbol Interference (ISI) which increases modem implementation loss. This paper presents modeling of the modem?s analog imperfections, an overview of the equalizer algorithm and FPGA architecture, plus analysis and simulation of the expected performance gain. Pre and post equalization results from the real time tests, including BER performance with different modulation schemes such as BPSK, QPSK and 8PSK are also shown.     

Vulcanization characteristics and mechanical properties of nitrile rubber filled with short leather fibres

Leather shavings have been used as filler in short fibre form for nitrile rubber reinforcement. Shavings neutralized with sodium bicarbonate and ammonia showed improved vulcanization characteristics and mechanical properties, whereas sodium hydroxide neutralized shavings exhibited poor properties. Swelling of the vulcanizates in water and 1% NaOH was found to increase with leather loading, whereas in MEK a reversed trend was observed. Thermogravimetric analysis indicates that the thermal stabilities of the vulcanizates fall between those of pure leather and gum nitrile rubber vulcanizate.     

Delay analysis of continuous bit rate traffic over an ATM network

A packet multiplexer is modeled for continuous bit rate (CBR) traffic in an asynchronous transfer mode (ATM) network as an nD/D/1 queue. The efficiencies of various algorithms for finding the delay distribution are compared. In particular, a new algorithm is proposed whose time complexity is O(n²), where n is the number of voice sources being multiplexed. The use of the central limit theorem can reduce the time complexity to O(n) for large n . An asymptotic formula is found whose time complexity is independent of n and it works well (for practical purposes) over a wide range of parameter values. The authors examine and comment on the use of the M/D/1 results as an approximation. In addition to comparing the performances of these algorithms, they show that the buffer requirements for such a queue are significantly less than the theoretical maximum (even when the requirement on the call disruption probability is very low). This result has important implications in the design of buffer size. The buffer requirement is relatively insensitive to the design criterion (call disruption probability)     

Anisotropic strength and deformational behavior of Himalayan schists

Anisotropy, which is characteristic of metamorphic rocks such as schists, is due to a process of metamorphic differentiation. Preferred orientation of minerals like mica and chlorite in response to tectonic stresses makes schistose rocks foliated. As a result their engineering properties vary with the direction of loading.The influence of transverse anisotropy on strength and deformational responses of four schistose rocks obtained from the foundation of two underground powerhouse sites in the Himalayas has been critically examined. Specimens at different orientation (β) of the foliations varying from 0° to 90° with respect to the axial stress (σ₁) in the unconfined state and also in the confined states up to 100 MPa of confining pressure were tested to evaluate the applicability of the non-linear strength criterion for the prediction of triaxial compressive strength and modulus. Based on the analysis of large experimental results it has been possible to predict strength and modulus with minimum pre-evaluation experimental data, i.e. only with three uniaxial compressive strength tests at 0°, 30° and 90° and two triaxial compression tests conducted at convenient confining pressures at β=90°orientation. Predicted non-linear stress–strain curves, using predicted values of strength and modulus have been found to match well with the experimental stress–strain curves even at higher confining pressures.     

Thermal behaviour of hollow-cored concrete slabs

This paper presents a detailed theoretical analysis of the thermal performance of hollow-cored concrete slabs. The governing equations are solved using appropriate boundary conditions and the results show that the heat flux entering the room through the roof is independent of the location of the air cavity within the depth of the slab.     

Asymmetric photoreactions within zeolites: role of confinement and alkali metal ions

In this Account strategies using zeolites as media to achieve chiral induction are presented. Diastereomeric excesses as high as 90% and enantiomeric excesses up to 78% have been obtained with selected systems within zeolites. The same systems show no asymmetric induction in solution. Chiral induction is dependent on the alkali ions present in the zeolites. Alkali ions control not only the extent of asymmetric induction but often the isomer being enhanced. Results of ab initio computations have allowed us to gain an insight into the observed selectivity within zeolites.     

Performance Analysis of Wire Electrodes on Machining Ti-6Al-4V Alloy using Electrical Discharge Machining Process

High-strength materials with complex shapes can be easily machined by electrical discharge machining process. In the present study, an attempt has been made to analyze the influence of wire electrode on Kerf width and workpiece surface roughness in wire EDM process. Due to its importance in the aircrafts and automobiles, Ti-6Al-4V alloy has been chosen as the workpiece material. The various experiments have been conducted based on a Taguchi L₉ orthogonal array with various types of wire electrodes, such as conventional brass wire, zinc-coated wire and diffused coated brass wire. From the experimental results, it has been observed that diffused coated wire produced better surface finish with minimum kerf width compared to the other two wire electrodes. It has also been observed that the pulse off-time has more influent nature on machining characteristics such as surface roughness and kerf width.     

Small Cell Planning: Resource Management and Interference Mitigation Mechanisms in LTE HetNets

In an attempt to address the huge data demand of indoor mobile users and poor signal strength from outdoor base stations to indoor environments, opertaors have started deploying variety of small cells likes Femtos, picos and micro cells. In this work, we used Femtos as small cells. Femto cells are low-cost, low-power consuming cellular base stations which operate only in licensed spectrum and are designed for both outdoor and indoor communication. Although small cells can be used for enhancing network capacity and coverage, arbitrary deployment of large number of small cells can lead to increase in operators expenditure and may create severe interference issues for cell edge users. In this paper, we look into optimal placement of small cell solutions to improve data rates of users in LTE HetNets using Femtos. Besides, these solutions address the main concerns of interference and resource management by proposing mechanisms for optimal placement of Femtos (OptFP, MinNF), dynamic power control and bandwidth allocation in Femtos (SOPC) and dynamic offloading. We provide a comparison of placement solutions and the applicability of each proposal keeping the operators’ revenue in mind.