karmano hy api boddhavyam boddhavyam ca vikarmanah akarmanas ca boddhavyam gahana karmano gatih The intricacies of action are very hard to understand. Therefore one should know properly what action is, what forbidden action is, and what inaction is. The Bhagvad Gita (4.17) This book is the outcome of the research contribution of Hanane Fathi towards her Ph.D. studies jointly with Shyam S. Chakraborty and Ramjee Prasad as - pervisors. To the best of the authors’ knowledge, this is a ?rst book on voice over Internet protocol (VoIP) covering such a broad perspective as illustrated in Figure P.1. This book is a new, forward-looking resource that explores the present and future trends of VoIP in the wireless heterogeneous networks. This book also provides the discovery path that these network infrastructures are following from a perspective of synergies with the present systems and how they will pave the way for future systems. This book is intended for everyone in the ?eld of wireless information and multimedia communications. It provides different levels of material suitable for managers, researchers, network providers, and graduate students. We hope that all readers will experience the bene?ts and power of this knowledge. We have tried our best to make each chapter comprehensive and we cannot claim that this book is without errors. Any remarks to improve the text and correct the errors would be highly appreciated.