The impressive growth of the Internet over the past years has resulted in constantly increasing demand for bandwidth. Hence, there is increased interest in new dynamic bandwidth trading mechanisms and more efficient ways of managing and charging the network resources. Also, the large growth of wireless networks, including the cellular networks, combined with the increasing demand for services, has resulted in increasing demand for the reservation of spectrum; this spectrum is required in order for these networks to provide 2nd (GSM), 2,5 (GPRS) and 3rd (UMTS) generation services. This book is both an overview of the state of the art of the applications of auction mechanisms in the telecoms sector and provides a guideline for researchers working in the field of mechanism design and network economics.