The idea for this book originated from a Special Session on Circuits and Systems for Future Generations of Wireless Communications that was presented at the 2005 InternationalSymposiumon Circuits and Systems, which was then followed by two Special Issues bearing the same title that appeared in the March and April 2008 issues of the IEEE Transactions on Circuits and Systems - Part II: Express Briefs. Out of a large number of great contributions, we have selected those tting best the book format based on their quality. We would like to thank all the authors, the reviewers of the Transactions on Circuits and Systems - Part II, and the reviewers of the nal book material for their efforts in creating this manuscript. We also thank the Springer Editorial Staff for their support in putting together all the good work. We hope that this book will provide you, the reader, with new insights into Circuits and Systems for Future Generations of Wireless Communications.