The Global System for Mobile Communication (GSM) is undoubtedly the most successful second generation digital mobile radio system. One of the key factors for this exceptional performance is the constant evolution of the GSM systems and its derivatives DCS-1800 and PCS-1900. The objective of the book is to address new concepts in the GSM system, dealing with both standardised features as well as theoretically and technologically feasible improvements, which contribute to evolutionary changes in general. Dynamic evolution of GSM presents a platform for the Universal Mobile Telecommunication System (UMTS) introduction and major trends in UMTS development will be addressed in this book, in particular progress towards new radio interface. The book is the collection of individual contributions from a number of authors. The intention of the editors was to gather the most prominent specialist in the GSM area. Ongoing efforts in GSM standardisation are focused on Phase 2+ with items planned to be added gradually on demand. Being mostly independent of each other, each of them could be introduced with little impact on the rest of the system. Speech remains the prime service of cellular systems with ongoing work on spectral efficiency taking into account the trade-off between cost of the system and transmission quality. Most notable result from novel speech service implementations is the introduction of new Enhanced Full Rate (EFR) speech coder. International railway organisation (Union Internationale des Chemins de Fer - UIC) has influenced the development of Advanced Speech Call Items (ASCI).