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August 15, 2004 Provided by System Dynamics Inc.

802.11a for Consumers: An Interview with Atheros Communications

We've long admired Atheros Communications, the leader in 802.11a Wi-Fi technology. During our family visit in California, we arranged to meet in person with Sheung Li, Product Line Manager, Home Networks, and Susanna Auyeung, Manager, Product Applications. We discussed the future of 802.11a, and looked at some technology advancements for consumer applications.

"Dual-mode" and "Tri-mode" Devices

802.11a operates in the 5 GHz frequency band, and was published as a standard in 1999 along with the slower 802.11b operating in the 2.4 GHz band. The popular 802.11g, standardized last year, is based on 802.11a, but operates in the same 2.4 GHz band as 802.11b. 802.11g devices always support 802.11b, and are called "dual-mode" devices. Newer "tri-mode" devices add 802.11a as well and operate in both frequency bands. Sheung told us that Atheros is the dominant supplier of chips used in tri-mode devices, and is second in dual-mode chips.

The 2.4 GHz band is quite congested, and consumers often experience interference from portable telephones, microwave ovens and other Wi-Fi networks operating in the same band. The 5 GHz band is much less congested, and has much more available bandwidth: 12 channels compared with the 3 effective channels in the 2.4 GHz band. So we've wondered when consumer products based on 802.11a would come to the market.

In the US at the present time, 802.11a is targeted to the large-enterprise market, while 802.11g is targeted to consumers and small business. Device manufacturers have charged a considerable premium for 802.11a and tri-mode access points, routers and LAN cards compared with dual-mode devices.

We asked Sheung what the underlying cost difference was between dual-mode and tri-mode devices. He wouldn't tell us the exact bill-of-materials (BOM) cost, but said the difference was "less than a Big Mac Value Meal", well under $5.00 here in New Jersey. In the US, the street price difference between dual-mode and tri-mode devices is much higher than that, so it didn't surprise us when Sheung said that in 2003, tri-mode devices represented only 11% of the Wi-Fi market.

Interestingly, he said we shouldn't view the US as being representative of the global Wi-Fi market. For example, he said "Japan is split 50/50." Part of the difference is the high concentration of apartments (5 GHz channels are much less congested than 2.4 Ghz), and part is pricing that better reflects the BOM difference. But the biggest difference is that "sales people in Japan SELL A/G" as a better long-term purchase, whereas sales people in the US sell only G.

We asked about the prospects for 802.11a in the consumer market, and Sheung said he expected Media Center PCs and Extenders to play a major role. MC Extenders are digital media adapters designed to move content from Media Center PCs to home TVs, scheduled to reach the market this fall. Because they are designed for high-quality video, they will work best with 802.11a. Sheung believes many manufacturers will include 802.11a support in Media Center PCs and Extenders.

Reference Designs and Consumer Devices

Susanna showed us Atheros reference designs and devices based on them. The reference designs were all based on the current AR5000 series--the "fifth generation" of Atheros 802.11a chip designs. We were intrigued by the tri-mode USB reference design based on the current AR5005UX chip set, which uses two Atheros chips: the AR5112 dual-band radio-on-a-chip which supports both 2.4 and 5 GHz transmit and receive; and the AR5523 multiprotocol MAC/baseband processor which does all the digital work. We also liked the tri-mode AR5005AP-X configurable access point reference design. These both show how small tri-mode devices are getting.

Susanna also showed us a sampling of consumer devices based on Atheros chips. We were especially amused by the "Mickey Fan" Wi-Fi access point and LAN card marketed by NTT in Japan.

Advanced Wireless Video Applications

We discussed the application of wireless networking for video applications--especially for high-definition video, which requires sustained speeds of about 20 Mbps. In the past, this has been nearly impossible for Wi-Fi devices, which experience a rapid falloff of speed from walls and floors between wireless devices, and often suffer from interruptions which would "break" the video.

Sheung showed us the specifications for their new chipset, the AR5005VA, a tri-mode device specifically designed for wireless video networking. This includes the full security features of the new 802.11i standard, has QoS features from the draft 802.11e standard, and is designed to interface directly with digital TV, DVD and DVR chipsets.

Atheros claims the chipset can "blanket homes up to 6,000 square feet with video-quality coverage". That's quite a claim, since current 802.11a devices don't come close to that range. Sheung said the new chipset has two features to enable greater range for video applications:

  • Multiple radio/smart antenna: The chipset supports multiple antennas for transmit beamforming and receive combining. This approach, often called multiple-input multiple-output (MIMO), is a key component of the 802.11n effort to create a super-high-speed successor to the current Wi-Fi standards.
  • Transmit speed backoff: Data-oriented devices attempt to transmit at the maximum possible speed, and tolerate occasional interruptions from interference, say by somebody walking between an access point and a portable device. TV does not work acceptably with interruptions. So the new chipset "backs off" from the maximum speed to a lower speed which will carry the TV content but which provides an added margin for interference.

Sheung showed us a demonstration of the new chipset. He said the chips are sampling now, and we should expect to see devices based on them at CES in January.

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