Beginning from an existing GSM circuit-switched voice base system network, there are two hardware upgrades in the base system for GPRS and EDGE. The first is a modification of the air (or Um) interface to support packet switching instead of circuit switching. In GPRS this is essentially just a protocol change, since the hardware aspects related to modulation are the same as GSM. Both GSM and GPRS use the same GMSK modulation. EDGE may require limited hardware changes in the base transceiver (depending on the specific internal hardware design), since the type of modulation is changed from GMSK to 8PSK.

The second upgrade is a packet-network-switching capability in the system infrastructure. This packet-switching capability extends end-to-end from the packet oriented mobile telephone, via the base station in the cell with the mobile data station, via the SGSN, through a suitable TCP/IP network, to the other participant in the packet communication. The SGSN switch for packet data is analogous to the MSC switch for voice. A packet-oriented mobile telephone may be a personal computer with a PCMCIA radio card, or a personal computer connected via a short data cable to a radio handset.

Various different configurations are permitted to install a gateway packet switch (GGSN). In theory, a GGSN could be designed and used so that it only handles packet traffic. For most installations, it is more likely that an existing MSC will be upgraded to handle both circuit-switched voice traffic and packet traffic.