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DSP power propels next-generation wireless

Posted: 15 Apr 2001 ?? ?Print Version ?Bookmark and Share

Keywords:dsp? wireless? gps? gprs?

The changing landscape of wireless design offers new opportunities along with tough technical challenges for designers. But without a doubt, DSPs will remain a fundamental part of wireless design.

For instance, the available bandwidth and the amount of information that can be crammed into that scarce resource limit wireless systems. That is where DSPs come in: data compression using advanced techniques, with the most obvious application in the voice-processing portion of cellular designs.

Voice codecs consume DSP instructions at a prodigious rate. The full-rate GSM first fielded in the early 1990s used about 10Mips of DSP for the voice codec function. To pack more calls into the available bandwidth, systems designers created a standard for half-rate GSM. While that strategy cut the data bit rate in half, it required nearly four times as many DSP MIPS to do the job. And each succeeding generation of cellular voice technology ups the DSP ante, with the amount of required digital signal processing increasing faster than the reduction in the data bit rate.

Even as the processing requirements rise for the voice codec function, the complete system requirements for products implementing 3G voice services increase the complexity yet again. In his contribution, Paul Marino, vice president and director of Motorola Inc.'s DSP Core Technology Center, notes that "just as voice codecs have continued to press the capabilities of programmable DSPs, the complexity required by 3G requirements is taxing the capabilities of traditional DSP technology and design methodologies. To meet these demands, next-generation DSP design programs have expanded from a focus on increased performance, lower power and manufacturing-process enhancements to enabling scalable, programmable and configurable DSP cores."

GPS is another application crying out for DSP power. Texas Instruments' Alan Gilkes, member of technical staff at the company's Wireless Communications Business Unit, forecasts widespread applications for low-cost, high-accuracy global positioning system modules. With 3G wireless communications bandwidth up to 2MBps, wireless applications soon will be able to download data and images at a faster transfer rate than most local-area networks can today, Gilkes said. The missing piece is to determine location. Applications abound vehicle tracking, business scheduling and a host of forward-looking uses. SoC devices that employ both a RISC CPU and a DSP are the proposed solution. The concept is driving toward a platform approach to DSP-based systems design.

Meanwhile, we are about to see a major shift of DSP technology toward broadcast-television signal processing, said Mohammad Ayub Khan, vice president for software and systems engineering at TriMedia Technologies Inc. Khan predicts TV will take on completely new design directions and characteristics based on very long-instruction-word (VLIW) media processing and software technologies. Long the brunt of dismissive comments, VLIW media processors are now streamlining, and they are advancing video/audio time shift applications originally supported by conventional controller processors and several DSP chips.

As fast as engineers determine how to apply today's DSP capabilities, wireless products are proliferating to the point where DSP suppliers are producing application-specific parts to meet unique needs. Predicting the winners may be next to impossible, but it is certain that DSP engineers will be the beneficiaries of vast amounts of processing power at low power and unbelievably low prices.

? Henry Davis


Henry Davis Consulting Inc.

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