Atheros' full end-to-end offering — with media-access controller, baseband and RF front end — together with the baseband/RF-only solution from Radiata open the door to full, IEEE 802.11a-compatible networking for the home and enterprise at data rates of up to 54 Mbits/second — five times that of 802.11b LANs of the preceding generation.

Their arrival could make the expected crowding of the 2.4-GHz band a nonissue. Presumably, OEMs can now train their sights on the clean, 5-GHz band without worrying about the added cost that until now kept that approach out of reach.

"These companies have done something I thought I wouldn't see for at least three years," said Craig Mathias, principal at the Farpoint Group (Ashland, Mass.). "The news totally changes everything, though its impact on 2.4 GHz probably won't be felt for another year as they ramp up production."

"No one has even managed to do 2.4 GHz in all-CMOS yet," said Stan Bruderle, chief analyst with Dataquest Inc. (San Jose). "Exotic and expensive silicon germanium or bipolar CMOS BiCMOS processes are still the norm. With 5 GHz in CMOS, there's no reason not to migrate to this band and take advantage of the higher rates, while at the same time avoiding the coexistence issues that are expected to plague the 2.4-GHz band in the near future as products roll out."

Along with packing a media-access controller (MAC), the Atheros solution differentiates itself by including what the company calls a "turbo mode" that allows it to operate at up to 75 Mbits/s. An optional low-noise-amplifier (LNA) boosts sensitivity for extended range.

No SAW filters are required, but a crystal oscillator and external filtering using low-cost resistor/capacitor networks are needed to complete the design.

"We have completely rearchitected the radio, and have taken a different approach that is shattering the price/performance barrier for wireless LANs," said Rich Redelfs, president and chief executive officer of Atheros. "This market is growing exponentially, and this could kick in the afterburners and redefine how WLANs are used."

The two Atheros chips, together dubbed the AR5000, are built in a 0.25-micron process and come in at less than $35 per set in quantities of 100,000. Sampling is to begin in the first quarter of next year, and Atheros expects to be in full production by the second quarter.

Unlike Atheros, Radiata has managed to integrate the voltage-controlled oscillators and all filtering on board. "All you need are bypass caps and resistors," said Chris Fisher, vice president of marketing at Radiata. Though officially minus a MAC, the company is in talks with a third-party supplier.

Radiata's "wireless engine" comprises a baseband modem (the R-M11a), done in a 0.25-micron process, and a 5-GHz radio transceiver (R-RF5) built in 0.18 micron. Like Atheros' offering, the total comes in under $35 per 100,000. However, Fisher expects that adding the MAC will bring the cost to $55. Sampling in October, the company expects to ramp to full production by January.

Band coverage

The Radiata solution covers the entire Unlicensed National Information Infrastructure (U-NII) band, from 5.15 to 5.25 GHz through 5.725 to 5.825 GHz. The AR5000 from Atheros covers only the frequency range from 5.15 through 5.35 GHz.

Both offerings integrate the analog-to-digital and digital-to-analog converters in the baseband, with Radiata specifying its devices at 80 samples/s.

The main problem both companies faced when looking at CMOS at 5 GHz was the instability of standard CMOS processes at high frequencies, resulting in lower yield and, therefore, higher cost. Also, CMOS tends to require more gain stages, hence more silicon area.

To get around these issues, the two companies — which said they knew nothing of the other's work — undertook a complete rethinking of how radios should be made. Both are being coy concerning details. Though sketchy, the information disclosed to date suggests solutions that are similar in some regards. Both, for example, used a digital signal processor to compensate for CMOS' inadequacies.

Radiata embedded a 32-bit microprocessor into the R-RF5, and used a set of algorithms to dynamically bias various circuits to do things like bias everything down to quiescent levels or a sleep mode.

Atheros wouldn't specify what kind of processor it used. "We have drawn on a core competency of the Atheros team to develop a more-efficient, low-power, proprietary design for our DSP processing," said Carl Temme, director of product management.

"We chose to characterize CMOS properly for high frequencies, which hasn't really been done to date, rather than opt to use an expensive non-CMOS process," Temme added.

Not everyone in the industry shares the companies' enthusiasm for CMOS, however. "Going to CMOS has its advantages, but SiGe processes scale much better in terms of power consumption vs. frequency," said Bent Hessen-Schmidt, vice president of marketing for SiGe Microsystems Inc. (Ontario). "In addition, the time-to-market advantages may be overrated, as CMOS foundries are currently overbooked."

Meanwhile, the two companies differ in their designs for their chip sets' front ends. Atheros' tack was to combine advanced direct-conversion techniques with the advantages of established superheterodyne architectures. According to Temme, "We rearchitected the radio to take advantage of the strong points of both technologies, but without their weaknesses."

To achieve 72-Mbit/s operation, or what the company calls turbo mode, the device uses two channels in the lower (200-MHz) region of the 5-GHz spectrum, instead of the full eight channels specified in 802.11a. "So while it's not a standards-compliant mode," said CEO Redelfs, "in a lot of environments, you don't need the full eight channels."

For its part, Radiata chose to stick with the tried and tested superheterodyne architecture, with multiple intermediate-frequency stages, but with "careful attention to frequency planning," said Fisher.

The result for both companies is low-power solutions that meet PCMCIA Type II power specifications (under 2 watts) and that can be fully implemented on just one side of the PCMCIA card.

Allen Nogee, senior analyst with Cahners In-Stat Group (Scottsdale, Ariz.), questions the technologies' line-of-sight requirements and range. "Orthogonal frequency-division multiplexing the type used in 802.11a hasn't been around very long, and at 5 GHz there is questionable wall-penetration capability — I'd like to see it in the office environment."

Another nagging question is how many access points would be needed in an office setting. "Up to twice as many as 802.11b may be required, raising serious cost-of-implementation concerns," said Nogee.