WLAN does without DSPs: TI promises to get there first - DSP-Mixed Signal Devices - business development for Texas Instruments' wireless networking business unit - Company Business and Marketing

Electronic News, Nov 11, 2002 by Gale Morrison

Wireless LAN (WLAN) signal processing is so demanding that the only silicon to handle it is hardwired custom logic and not general-purpose DSPs, as most might expect.

"DSPs just draw too much power for the portable applications," said Carter Horney, a WLAN researcher associated with DSP researcher Will Strauss and his company, Forward Concepts. "The majority of the wireless LAN chipset market is the PC laptop."

Horney said he cannot be 100 percent sure that no WLAN IC vendor uses a DSP because these things are kept close to the vest. The market right now is relatively small and captive, he said. "But it's unlikely because it just takes too much power," Homey said.

Yoram Solomon, director of business development for Texas Instruments' wireless networking business unit, confirms that even TI, the top DSP company, does not use a DSP for WLAN.

"Nobody does," Solomon said. "Why can't we do it in software? It's really a Moore's Law thing. Take for example an analog, dialup modem. The signal processing has to handle 8,000 samples per second ... it took years for Pentium to be able to do that. In 1997, we weren't sure it could.

"In the wireless LAN space, you are talking 40, 44, 80, let's say 80 to 160 million samples per second. That's a different ball game," Solomon said. "Can you use a fully software programmable, general-purpose DSP to do that?

"You don't have that processor today," he said. "At 160 megasamples per second--we don't have that DSP yet. That's not one instruction per sample, it's more than one instruction."

Of course TI made sure this doesn't keep the company from owning a piece of the WLAN market. The Dallas-based DSP giant bought WLAN specialist Alantro to enter the space, and Homey said it has since taken a healthy 10 percent share of the market. Intersil leads now with a whopping 60 percent-plus share.

"It's not just a matter of being power-hungry, you don't have that processor today. But obviously it's a matter of time," Solomon said. "When we get to the right [fab] processing point and the milliwatts per MIPS that a DSP has is low enough, you are going to see a natural transition.

"I have to say that TI is probably going to be the first one there," Solomon said jokingly. "But that's because I'm not biased."

Solomon said that in his previous jobs at host signal processing pioneer PCTEL, TI in fact helped the company figure out that only hardware acceleration could do the WLAN processing task.

"I was shopping around to get a DSP to do wireless LAN--even going to TI and asking them," he said. "They were using Ph.D.s to try and figure out the processing power that needs. Everyone found that what you do is just accelerate the hardware (in custom logic). That's not really a DSP--it's a state machine with some multiply, accumulate and compare function--but nothing beyond that."

So that means the baseband in WLAN is still up for grabs, but Homey says the media access control (MAC) function is definitively ARM.

"On the MAC side everybody uses some form of ARM," Horney said. "Either ARM7 or ARM9." He adds that the anti--"hot new startup"--Idaho's Atmel--is coming on very strong in the MAC space, with the help of its partnership for supply with RF Micro Devices.

Solomon reiterated his belief that TI will be first with a true DSP programmed for WLAN.

"TI really is a DSP company," Solomon said. "We're always researching. We're shrinking the sizes of DSPs and improving the ratio of MIPS to milliwatts. We're going to be the first one coming out with a pure software-defined radio for wireless LAN."