High Speed Circuit Switched Data, HSCSD
The standard GSMTM circuit-switched connection offers a data rate much too low for sophisticated web browsing and the transfer of large files, and as early as Release 96 of the GSM specifications it was realized that a significant increase in speed could be obtained by aggregating two or more channels into a single, grouped, circuit-switched connection.
The specifications (3GPPTM TS 22.034 requirements, 23.034 architecture) allow for up to four channels to be combined, giving 57.6 kbit/s (or 38.4 kbit/s in the USA). The service is known as High Speed Circuit Switched Data, HSCSD.
Since the four channels are tied up in a circuit-switched connection, the network operator is likely to charge an HSCSD call at a considerably higher rate than a simple, single channel call, and the service was never enormously popular. HSCSD has been largely replaced by the General Packet Radio Service (GPRS) and Enhanced Data rates for Global Evolution (EDGE), which are more versatile, offer higher data rates, and are more economical.