GSM common data services are based on the circuit switching technology with maximum transmission data rate 9.6 kbps. In the upgrade of GSM network (phase 2+) ETSI defined new and faster style of data transfer. One of the main characters of GSM phase 2+ is GPRS and HSCSD standard. While the HSCSD standard represents application of circuit switching in data transfer, GPRS standard is the technology, which uses packet switching. Both standards represent 2.5-generation standard.
In HSCSD (High Speed Circuit Switched Data) standard is the data transfer realized without error correction code. This makes possible to increase data rate from 9.6 kbps to 14.4 kbps per channel. HSCSD standard also supports time slots combination and final data rate is a combination of 9.6 kbps or 14.4 kbps channels. Operators will be able to provide variant data rates from 9.6 kbps to 57.6 kbps. Operators can achieve data rates up to 200 kbps with the data compression. HSCSD standard has possibility to provide an asymmetric and symmetric data traffic. In term of resource allocation, HSCSD standard is not effective for packet data transfer, because resources are allocated only in time when the packet transfer is required.
ETSI made a standardization of a new service in GSM phase 2+. This service is based on a packet switching and it is called GPRS (General Packet Radio Service). GPRS speeds up data rates in GSM network, provides a better compatibility with LAN and WAN networks and with Internet. GPRS network uses radio resources only in a case when the data are received or sent. GPRS network provides immediate connection and high level of throughput. Whereas GSM system was originally designed for voice services, the main goal of GPRS network is to offer the access to standard data networks, working under TCP/IP protocol. GPRS network is a sub network of such networks.