This fully updated second volume of the highly successful WWRF Book of Visions is a unique and timely book, presenting up-to-the-minute ideas and trends in mobile communications. This is a comprehensive single point of reference, focusing on the specifications and requirements of 4G and identifying potential business models, the research areas and required spectrum and enabling technologies. Comprising material from White Papers edited within the working expert groups as well as those from the Vision Committee of WWRF, a top-down approach has been adopted starting from perceived users requirements and their expectations in the Future Wireless World.