High Speed Packet Access (HSPA) is a generic term to refer to improvements in the UMTS Radio Interface. HSPA refers to both improvements made in the downlink, often referred to as High Speed Downlink Packet Access (HSDPA) and to improvements made in the uplink, often referrred to as High Speed Uplink Packet Access (HSUPA).
Only the radio access network, notably the base stations (Node B) has to be modified to implement HSPA. There aren't any modifications necessary in the core network. The user will require a new terminal.