Femtocells may well change the shape and operation of mobile networks over the next few years. These compact devices (the size of a paperback book) combine the functionality of a 3G mobile cellsite, broadband DSL modem and WiFi hotspot all in one. They are going through operator trials and should be commercially available in many markets during 2009. As with mobile phones, they must be sold in conjunction with a mobile phone operator because they use licenced spectrum. Initially, they are likely to be subsidised as part of a package deal. This book explains the technology, describes the key vendors, suggests likely business models and provides insights into this exciting new development of mobile networks.