Periodic structures are of great importance in electromagnetics due to their wide range of applications such as frequency selective surfaces (FSS), electromagnetic band gap (EBG) structures, periodic absorbers, meta-materials, and many others. The aim of this book is to develop efficient computational algorithms to analyze the scattering properties of various electromagnetic periodic structures using the finite-difference time-domain periodic boundary condition (FDTD/PBC) method. A new FDTD/PBC-based algorithm is introduced to analyze general skewed grid periodic structures while another algorithm is developed to analyze dispersive periodic structures. Moreover, the proposed algorithms are successfully integrated with the generalized scattering matrix (GSM) technique, identified as the hybrid FDTD-GSM algorithm, to efficiently analyze multilayer periodic structures. All the developed algorithms are easy to implement and are efficient in both computational time and memory usage. These algorithms are validated through several numerical test cases. The computational methods presented in this book will help scientists and engineers to investigate and design novel periodic structures and to explore other research frontiers in electromagnetics. Table of Contents: Introduction / FDTD Method and Periodic Boundary Conditions / Skewed Grid Periodic Structures / Dispersive Periodic Structures / Multilayered Periodic Structures / Conclusions

LDPC Codes are considered to be serious competitors to turbo codes in terms of performance and complexity. They are specified by a sparse parity check matrix containing mostly 0s and relatively few 1s. In this book, LDPC codes used in the IEEE 802.16 standard physical layer were studied. Two novel techniques to enhance the performance of such codes are introduced. In the first technique, a novel parity check matrix for LDPC codes over GF(4) is proposed based on the binary parity check matrix used in the IEEE 802.16 standard . The proposed code has proven to outperform the binary code used in the IEEE 802.16 standard over both AWGN and SUI-3 channel model. In the second technique, high rate LDPC code is used, in a concatenated coding structure, as an outer code, with a convolutional code as an inner code. The performance of such a concatenated codes is compared with the commonly used one utilizing Reed-Solomon codes over the standard SUI-3 channel model, and show better performance.