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Texas Instruments last month introduced the industry's first implementation of software for half-rate Global System for Mobile Communications (GSM) wireless communications. Like the full-rate GSM software that TI introduced in May, the new offering helps shorten time-to-market for efficient, cost-effective applications employing the standard.
The fully tested, half-rate GSM software modules are designed to run most efficiently on TI's TMS320C545 and TMS320C546 Digital Signal Processors (DSPs). These two devices, optimized for cellular telephone applications, also were introduced in September (See Winning wireless).
While GSM is just one of several standards that may be implemented in a half-rate configuration, it is widely used in Europe and Asia and may play a role in the introduction of personal communications services in the United States. Half-rate standards help telephone service providers pack more conversations into existing bandwidth. They also facilitate simultaneous voice and data communications.
TI's half-rate GSM software modules perform voice coding and decoding, demodulation, encryption, channel coding and decoding, interrupt handling and control and other functions. The software requires only 27 MIPS of the 50 MIPS processing capacity available on the 'C545 and 'C546, leaving ample performance for such features as voice dialing, speaker phone and noise cancellation.
"When TI's half-rate GSM software runs on a 'C545 or 'C546, it operates so efficiently that it can easily implement all baseband digital signal processing functions, even for this fairly complex version of the standard," says Edgar Auslander, TI's European wireless DSP manager. "The remaining MIPS allow many tasks traditionally handled by ASICs or microcontrollers to be integrated into the DSP, lowering overall system cost." The half-rate GSM software is available for licensing.
October 1995, vol. 12, no. 7