O-Arylation of Iodophenols with 2-Fluorobenzaldehyde Under Microwave Conditions

The arylation of 4-iodo-, 2-iodo- and 3-iodophenols with 2-fluorobenzaldehyde may be carried out in the presence of K2CO3 in DMF as the solvent under microwave conditions. The arylation of 4-iodophenole was promoted by the use of triethylbenzylammonium chloride (TEBAC) as the phase transfer catalyst. In the other model reactions, the use of TEBAC was harmful. By-products formed by isomerization and disproportionation were also detected

Synthesis of Real Weyl-Heisenberg Signal Frames with Desired Frequency-Time Localization

An algebraic approach to the synthesis of optimal real Weyl-Heisenberg frames with the best frequency-time localization oriented to the processing of discrete signals is developed. The chosen optimality criterion ensures the construction of a tight signal frame with the lowest standard deviation of frame functions from the desired standard. In addition, a special algebraic structure of the synthesis algorithm in the form of a product of sparse matrices allows for efficient computational implementation and flexible adjustment of the frequency-time resolution of the signal functions of the frame. The results of the experiment confirming the effective computational implementation of the algorithm and a desired time-frequency localization of frame functions are presented

Generation of correlated Rayleigh fading channels for accurate simulationof promising wireless communication systems

In this paper, a generalized method is proposed for the accurate simulation of equal/ unequal power correlated Rayleigh fading channels to overcome the shortcomings of existing methods. Spatial and spectral correlations are also considered in this technique for different transmission conditions. It employs successive coloring for the inphase and quadrature components of successive signals using real correlation vector of successive signal envelopes rather than complex covariance matrix of the Gaussian signals which is utilized in conventional methods. Any number of fading signals with any desired correlations of successive envelope pairs in the interval [0, 1] can be generated with high accuracy. Moreover, factorization of the desired covariance matrix is avoided to overcome the shortcomings and high computational complexity of conventional methods. Extensive simulations of different representative scenarios demonstrate the effectiveness of the proposedtechnique. The simplicity and accuracy of this method will help the researchers to study and simulate the impact of fading correlation on the performance evaluation of various multi-antenna and multicarrier communication systems. Moreover, it enables the engineers for efficient design and deployment of new schemes for feasible wireless application