High speed mobile data will certainly improve the existing mobile networks greatly. GPRS and EDGE, in particular, will write a new chapter in mobile communications history. Currently, almost all network operators worldwide are upgrading their GSM networks in order to provide high speed mobile data to their subscribers. HSCSD is a circuit-switched technology. Therefore, one of its major advantages is that the existing core network, mainly the MSC, is able to handle HSCSD traffic. As opposed to GPRS, HSCSD neither requires a hardware upgrade within the network, nor does it introduce new channel coding technologies. Therefore, HSCSD is a rather simple upgrade of the standard GSM, particularly in comparison with GPRS and EDGE.