LTE Advanced: Technology and Performance Analysis

Wireless data usage is increasing at a phenomenal rate and driving the need for continued innovations in wireless data technologies to provide more capacity and higher quality of service. In October 2009, 3rd Generation Partnership Project (3GPP) submitted LTE-Advanced to the ITU as a proposed candidate IMT-Advanced technology for which specifications could become available in 2011 through Release-10 . The aim of “LTE-Advanced” is to further enhance LTE radio access in terms of system performance and capabilities compared to current cellular systems, including the first release of LTE, with a specific goal to ensure that LTE fulfills and even surpass the requirements of “IMT-Advanced” as defined by the International Telecommunication Union (ITU-R) . This thesis offers an introduction to the mobile communication standard known as LTE Advanced, depicting the evolution of the standard from its roots and discussing several important technologies that help it evolve to accomplishing the IMT-Advanced requirements. A short history of the LTE standard is offered, along with a discussion of its standards and performance. LTE-Advanced details include analysis on the physical layer by investigating the performance of SC-FDMA and OFDMA of LTE physical layer. The investigation is done by considering different modulation schemes (QPSK, 16QAM and 64QAM) on the basis of PAPR, BER, power spectral density (PSD) and error probability by simulating the model of SC-FDMA & OFDMA. To evaluate the performance in presence of noise, an Additive White Gaussian Noise (AWGN) channel was introduced. A set of conclusions is derived from our results describing the effect of higher order modulation schemes on BER and error probability for both OFDMA and SC-FDMA. The power spectral densities of both the multiple access techniques (OFDMA and SC-FDMA) are calculated and result shows that the OFDMA has higher power spectral density.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Mechanochemical Defluorinative Arylation of Trifluoroacetamides : An Entry to Aromatic Amides

The amide bond is prominent in natural and synthetic organic molecules endowed with activity in various fields. Among a wide array of amide synthetic methods, substitution on a pre-existing (O)C-N moiety is an underexplored strategy for the synthesis of amides. In this work, we disclose a new protocol for the defluorinative arylation of aliphatic and aromatic trifluoroacetamides yielding aromatic amides. The mechanochemically induced reaction of either arylboronic acids, trimethoxyphenylsilanes, diaryliodonium salts, or dimethyl(phenyl)sulfonium salts with trifluoroacetamides affords substituted aromatic amides in good to excellent yields. These nickel-catalyzed reactions are enabled by C-CF3 bond activation using Dy2O3 as an additive. The current protocol provides versatile and scalable routes for accessing a wide variety of substituted aromatic amides. Moreover, the protocol described in this work overcomes the drawbacks and limitations in the previously reported methods.Peer reviewe

Mechanochemical Transformation of CF3 Group : Synthesis of Amides and Schiff Bases

We communicate two mild, solvent-free mechanochemical coupling transformations of CF3 group with nitro compounds into amides or Schiff bases employing Ytterbia as a catalyst. This process proceeds via C-F bond activation, accompanied with utilisation of Si-based reductants/oxygen scavengers - reductants of the nitro group. The scope and limitations of the disclosed methodologies are thoroughly studied. To the best of our knowledge, this work is the first example of mechanical energy promoted transformation of the inert CF3 group into other functionalities.Peer reviewe

Mechanochemical Conversion of Aromatic Amines to Aryl Trifluoromethyl Ethers

Increased interest in the trifluoromethoxy group in organic synthesis and medicinal chemistry has induced a demand for new, selective, general, and faster methods applicable to natural products and highly functionalized compounds at a later stage of hit-to-lead campaigns. Applying pyrylium tetrafluoroborate, we have developed a mechanochemical protocol to selectively substitute the aromatic amino group with the OCF3 functionality. The scope of our method includes 31 examples of ring-substituted anilines, including amides and sulfonamides. Expected SNAr products were obtained in excellent yields. The presented concise method opens a pathway to new chemical spaces for the pharmaceutical industry.Peer reviewe

Mechanochemical Ni-Catalysed Arylation of Ortho-Hydroxyarylenaminones : Synthesis of Isoflavones

This work describes two new synthetic methods for the preparation of isoflavones following the Ni-catalysed domino arylation reactions of the vast range of ortho-hydroxyarylenaminones utilising aromatic bromides as well as carboxylic acids. The presented protocols tolerated significant variation of all coupling partners and enabled synthesis of isoflavone library of twenty-three representatives. This is the first communicated precedent where the mechanic energy was utilised in the synthesis of isoflavones following the domino cyclisation mode.Peer reviewe

Exploration of new sustainable synthetic methods for the synthesis of fused pyridines and 4-quinolones based on the domino reaction of chromones and other masked dielectrophiles with nucleophiles

The present work aimed to study the big potential of chromone derivatives and 1-(2-fluorophenyl)prop-2-yn-1-ones for the synthesis of purine-like fused pyridines and 4-quinolone derivatives. In this regard, a wide range of substituents and substitution patterns are tolerated in the reaction. In addition a new and easy way for synthesis of 4-quinolone derivatives and other fused systems via domino cycloaddition reactions of ortho-fluoro substituted benzoylchromones, 1-(2-fluorophenyl)prop-2-yn-1-ones and aliphatic or aromatic amines were developed

Cu-Catalyzed Arylation of Bromo-Difluoro-Acetamides by Aryl Boronic Acids, Aryl Trialkoxysilanes and Dimethyl-Aryl-Sulfonium Salts : New Entries to Aromatic Amides

We describe a mechanism-guided discovery of a synthetic methodology that enables the preparation of aromatic amides from 2-bromo-2,2-difluoroacetamides utilizing a copper-catalyzed direct arylation. Readily available and structurally simple aryl precursors such as aryl boronic acids, aryl trialkoxysilanes and dimethyl-aryl-sulfonium salts were used as the source for the aryl substituents. The scope of the reactions was tested, and the reactions were insensitive to the electronic nature of the aryl groups, as both electron-rich and electron-deficient aryls were successfully introduced. A wide range of 2-bromo-2,2-difluoroacetamides as either aliphatic or aromatic secondary or tertiary amides were also reactive under the developed conditions. The described synthetic protocols displayed excellent efficiency and were successfully utilized for the expeditious preparation of diverse aromatic amides in good-to-excellent yields. The reactions were scaled up to gram quantities.Peer reviewe

Application of Silicon-Initiated Water Splitting for the Reduction of Organic Substrates

The use of water as a donor for hydrogen suitable for the reduction of several important classes of organic compounds is described. It is found that the reductive water splitting can be promoted by several metalloids among which silicon shows the best efficiency. The developed methodologies were applied for the reduction of nitro compounds, N‐oxides, sulfoxides, alkenes, alkynes, hydrodehalogenation as well as for the gram‐scale synthesis of several substrates of industrial importance

Nanocellulose as Convenient Reaction Media for the FeCl₃ Mediated Mechanochemical Synthesis of 3‑Acylchromones

A solvent free strategy for the mechanochemical synthesis of 3-acylchromones has been developed via FeCl3-nanocellulose mediated dehydrative coupling of ortho-hydroxyarylenaminones and carboxylic acids. The ortho-hydroxyarylenaminones undergo electrophilic domino cyclization followed by an unusual acylation event with carboxylic acids in the presence of FeCl3 as the catalyst and nanocellulose as the reaction media. The protocol was found to be simple, efficient, and environmentally benign to obtain a diverse array of 3-acylchromones with high yields. The protocol features advantages such as the use of cheap and readily available carboxylic acids as acyl source and no requirement of directing groups, oxidants, and solvents. Furthermore, the utilization of a wood-derived material, nanocellulose as the biodegradable reaction media and nontoxic iron salt as the catalyst under very mild and solvent-free conditions makes this acylation protocol very interesting in the perspective of the Green Chemistry principles