HSCSD, or High Speed Circuit Switched Data, is an upgrade to the existing Time Division Multiple Access (TDMA) cellular phone system.

What is HSCSD (High Speed Circuit Switched Data)?

An upgrade to the existing Time Division Multiple Access (TDMA) cellular phone system. High Speed Circuit Switched Data (HSCSD) provides subscribers with up to four separate 14.4-Kbps communication channels that can be bundled together to provide greater bandwidth for data transmission.

However, the overhead that is required by this bundling results in bandwidth of only 28.8 Kbps instead of the theoretical 57.6 Kbps. Unlike General Packet Radio Service (GPRS), which requires that existing TDMA hardware be upgraded, HSCSD is a software-only upgrade.

Some operators of Global System for Mobile Communications (GSM) cellular networks have upgraded their systems to HSCSD. However, competition from GPRS, which will be ready for deployment in the year 2000, could slow the growth and adoption of HSCSD technologies and eventually overshadow them.

HSCSD is also an option in Enhanced Data Rates for GSM Evolution (EDGE) and Universal Mobile Telecommunications System (UMTS) systems where packet data transmission rates are much higher. In the UMTS system, the advantages of HSCSD over packet data are even lower since the UMTS radio interface has been specifically designed to support high bandwidth, low latency packet connections. This means that the primary reason to use HSCSD in this environment would be access to legacy dial up systems.