a suitable book structure has been the most demanding issue. For the main author it has taken years to acquire a reasonable conviction. Often, the evolving conviction tends to successively upgrade business aspects on behalf of technology, in order to justify the title word 'Understanding'. Understanding is also firmly related to a pronounced pedagogical goal of the book. Finding a good book structure for a broad subject is similar to building a house with a number of rooms for different purposes. Filling the chapters with content then corresponds to furnishing the rooms. Changing the rooms is difficult and expensive. Changing the furnishing is easier and mistakes can more easily be corrected. New modern furniture can replace older inventories. To make the structure issue even trickier, the telecom complexity of today requires different types of 'rooms': Functional rooms devoted to a specific purpose, such as security or quality of service. More hardware and implementation oriented rooms, such as access and control equip- ment and its capabilities. Process flow oriented rooms, where we can identify the users, the various service providers (in a broad sense) and their planning, implementation and management, the technical development tracks and the related business models. The main references mentioned in the reference section concern the important struc- turing of the 'house'. The 'room furniture' may be continuously changed, following the new standards from bodies such as 3GPP, ITU, IETF, ETSI and many others. Evidently, a book with a fairly long production time like this one cannot include all the latest 'furniture'. However, the web often provides information on new standards. About the Author Anders Olsson has worked for many years as a network designer in Sweden (Televerket, nowadays TeliaSonera), Colombia (Telecom) and Tanzania (TP & TC), and in 1991 was appointed senior expert in Network oriented training at Ericsson. References and Acknowledgements FUNCTIONAL STRUCTURE AND RELATED ACKNOWLEDGEMENTS The most