Hitachi's SH-DSP improves efficiency of GSM handsets

Hitachi’s SH-DSP improves efficiency of GSM handsets
Richard Ball Hitachi has set up a mobile phone demonstrator using its SH-DSP, its Risc/DSP microprocessor. The system is said to be smaller, more efficient and hence cheaper than existing solutions. Conventional GSM mobile phone handsets contain two processors: a microcontroller and a DSP. The former handles the protocol stack and the man-machine interface. The DSP carries out the coder/decoder functions converting speech and data into the I/Q baseband signal. This arrangement, Hitachi argues, is inefficient, requiring more memory and complex message passing as well as physical buffers between processors. Removing these problems will help, especially in the future when more data is sent to and from mobile phones. The company’s demonstrator only handles layer one (physical) of the GSM protocols. “Most of the time critical software is included in layer one. We’re talking about 90 per cent of the loading,” said Chris Litchfield, Hitachi’s marketing manager. The total processing carried out by the SH-DSP amounts to 23Mips, leaving 30Mips for other functions. Another bonus for systems developers is that programming involves using a single set of tools. Assembler code for the DSP functions is placed in-line with C microcontroller code.

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