Mapper and Demapper for LDPC-Coded Systems

Low Density Parity Check (LDPC) codes are state-of-art error correcting codes, included in several standards for broadcast transmissions. Iterative softdecision decoding algorithms for LDPC codes reach excellent error correction capability; their performance, however, is strongly affected by finite-precision issues in the representation of inner variables. Great attention has been paid, in recent literature, to the topic of quantization for LDPC decoders, but mostly focusing on binary modulations and analyzing finite precision effects in a disaggregrated manner, i.e., considering separately each block of the receiver. Modern telecommunication standards, instead, often adopt high order modulation schemes, e.g. M-QAM, with the aim to achieve large spectral efficiency. This puts additional quantization problems, that have been poorly debated in previous literature. This paper discusses the choice of suitable quantization characteristics for both the decoder messages and the received samples in LDPC-coded systems using M-QAM schemes. The analysis involves also the demapper block, that provides initial likelihood values for the decoder, by relating its quantization strategy with that of the decoder. A signal label for a signal in a 2m-ary modulation scheme is simply the m-bit pattern assigned to the signal. A mapping strategy refers to the grouping of bits within a codeword, where each mbit group is used to select a 2m-ary signal in accordance with the signal labels. The most obvious mapping strategy is to use each group of m consecutive bits to select a signal. . We will call this the consecutive-bit (CB) mapping strategy. An alternative strategy is the bit-reliability (BR) mapping strategy which will be described below. A new demapper version, based on approximate expressions, is also presented, that introduces a slight deviation from the ideal case but yields a low complexity hardware implementation

Nanoindentation studies on waveguides inscribed in chalcogenide glasses using ultrafast laser

Optical straight waveguides are inscribed in GeGaS and GeGaSSb glasses using a high repetition-rate sub-picosecond laser. The mechanical properties of the glasses in the inscribed regions, which have undergone photo induced changes, have been evaluated by using the nanoindentation technique. Results show that the hardness and elastic modulus of the photo-modified glasses are significantly lower as compared to the other locations in the waveguide, which tend to be similar to those of the unexposed areas. The observed mechanical effects are found to correlate well with the optical properties of the waveguides. Further, based on the results, the minimum threshold values of hardness and elastic modulus for the particular propagation mode of the waveguide (single or multi), has been established

Weldability of Friction Stir Welding using Aluminium Alloy with Pure Copper

Recently many reports on Friction Stir Welding (FSW) of various dissimilar systems such as Aluminium to Copper been reported.FSW of Aluminium, Copper has captured important attention from manufacturing industries, such as Shipbuilding, Automotive, Railway and Aircraft production. Copper and its alloys are widely used in industrial applications due to their excellent electrical & thermal conductivities, good strength, corrosion & fatigue resistance. The aim of present study was analogy of the microstructures and mechanical properties of friction stir welded joint of Aluminium to Copper plates in 4mm thickness

BEP Performance Analysis of Multi-Node Self Encoded Spread Spectrum - Cooperative Diversity in Rayleigh Fading Channel

Self - encoded spread spectrum (SESS) is a novel modulation technique th at acquires its spreading sequence from the random input data stream rather than through the use of the traditional pseudo - noise code generator. It has been incorporated with multi node cooperative diversity systems as a means to combat fading in wireless channels. In this paper we analyze the cooperative SESS for Amplify and Forward CD links ( M SESS - AFCD) and SESS for Decode and forward CD links ( M SESS - DFCD) in Rayleigh fading channels. The BE P expressions are derived in closed form, and the veracity of the analysis is confirmed by numerical calculations that demonstrate excellent agreement with simulation results

Optimising Fault Tolerance in Real-time Cloud Computing IaaS Environment

YesFault tolerance is the ability of a system to respond swiftly to an unexpected failure. Failures in a cloud computing environment are normal rather than exceptional, but fault detection and system recovery in a real time cloud system is a crucial issue. To deal with this problem and to minimize the risk of failure, an optimal fault tolerance mechanism was introduced where fault tolerance was achieved using the combination of the Cloud Master, Compute nodes, Cloud load balancer, Selection mechanism and Cloud Fault handler. In this paper, we proposed an optimized fault tolerance approach where a model is designed to tolerate faults based on the reliability of each compute node (virtual machine) and can be replaced if the performance is not optimal. Preliminary test of our algorithm indicates that the rate of increase in pass rate exceeds the decrease in failure rate and it also considers forward and backward recovery using diverse software tools. Our results obtained are demonstrated through experimental validation thereby laying a foundation for a fully fault tolerant IaaS Cloud environment, which suggests a good performance of our model compared to current existing approaches.Petroleum Technology Development Fund (PTDF

Multi User Diversity Evaluation in MIMO HSDPA Downlink Channels

A multiple transmit antenna, single receive antenna (per receiver) downlink channel with limited channel feedback is considered. Given a constraint on the total system-wide channel feedback, the following question is considered: is it preferable to get low-rate feedback from a large number of receivers or to receive high-rate/high-quality feedback from a smaller number of (randomly selected) receivers. Acquiring feedback from many users allows multi-user diversity to be exploited, while highrate feedback allows for very precise selection of beamforming directions. It is shown that systems in which a limited number of users feedback high-rate channel information significantly outperform low-rate/many user systems. The marginal benefit of channel feedback is very significant up to the point where the CSI is essentially perfect

WATER CARRIER

The main aim of our project is to develop a mechanism for easy transportation of more water at a time from water pond, rivers, etc. , to their respective places. Water place a vital role in our daily life. Water is the major requirement in our day to day life, without water we can't do anything. Locally water will be carrying by women's from miles of distances to therehomes. Women's are used to carry the water on their head, while carrying the water on their heads, it causes the major effect on their spinal cord. To overcome this problem for women's we re- implemented this project for easy to carry of water. If they are tired ,While carrying of water they can take the rest under the metal sheet which is placed on the top of the carrier. It is also used to protect the carrier from the sun ray's. The main aim to develop this is, to help the women's who are carrying the water on their heads and to protect them from the injuries and causes from carrying of water on their heads