The speech transcoding frame 2000 for GSM cellular systems

The Global System for Mobile Communications (GSM) is the leading digital mobile telephone standard in the world. This paper describes the GSM cellular system, its features and services, and its system architecture. It also details the Speech Transcoding Frame (STF) 2000, one component of Lucent Technologies' GSM system. The STF 2000, which provides speech encoding and decoding (known collectively as “transcoding”) and data rate adaptation, is cost effective, with a flexible, modular architecture that allows gradual system growth and enhancements with little or no downtime. It has the capability for “half-rate” speech coding, which enables network operators to double their over-the-air capacity without the need for increased radio-frequency (RF) spectrum. The system includes a notebook PC with a graphical user interface that simplifies installation, maintenance, and on-site diagnostics. Fault-recovery software enables the STF 2000 to recover automatically from internally and externally detected faults. Redundancy is built into critical system components so that standby or spare components can be switched into service when there is a fault in the active component. GSM features such as discontinuous transmission increase the system efficiency by decreasing radio interference and saving battery power at mobile stations. The STF 2000 meets European telecommunications standards.