General Packet Radio Service is a major upgrade to GSM and therefore, an entire chapter deals with all details of GPRS. We will make you familiar with all aspects of GPRS, starting with new concepts like Quality of Service or the packet data channels. GPRS also introduces a new protocol stack that you will find in this chapter. However, the most important aspect of GPRS is the "Resource on Demand" concept that becomes most obvious when you view the details of the important scenarios of GPRS in this chapter.