Marvell promotes flexibility in 802.11g chipsets

Marvell promotes flexibility in 802.11g chipsets
By Robert Keenan, EE Times
February 24, 2003 (1:11 p.m. EST)
URL: http://www.eetimes.com/story/OEG20030224S0029

ROCHESTER, N.Y. — Hoping to pick up where others have faltered, Marvell will unveil an 802.11g-version of its Libertas chipsets this week. The company promises they will provide backward compatibility with existing 802.11b designs while offering compatibility with the 802.11g spec once it is formally approved.

Hype surrounding the 802.11g specification has been building since just before the Comdex show, with both chip developers and OEMs touting their 802.11g solutions. As 802.11g gains steam, questions are also surfacing about potential interoperability problems between existing 802.11g systems on the market and these and incumbent 802.11b systems.

According to James Chen, Marvell product marketing manager, since some of the initial 802.11g systems are based on an older draft 802.11g spec, they can either knock out or reduce the throughput on existing 802.11b channels. "The current 802.11g systems on the market and 802.11 systems just do n't play nice together," Chen said.

One reason that problems occur between with 802.11g and b devices could be in the version of the 802.11g spec implemented at the chip level. Chen said most available chipsets are based on draft specs that could be as much as six months old, resulting in potential interoperability problems. Chen added that the use of the older draft specs could also lead to compliance problems for existing products with the final ratified version of the 802.11g spec.

Marvell is hoping to curb both the interoperability and compliance problems with the release of two chipsets—one for client devices and one for access points. Part of the Libertas family, the client side chipset combines the 88W8310 digital chip with the 88W8010 RF front-end chip while the AP solution includes the 88W8510 digital chip as well as the same RF front-end IC in the client chipset.

To address potential compliance and interoperability issues, Marvell developed the 88W8510 and 88W8310 digital chips a round a flexible ARM9 architecture. According to Chen, Marvell's ARM9 core has been developed to provide flexibility through firmware updates. "Our ARM9 is pretty much a firmware machine," he said.

By offering the ability to offer firmware upgrades, Marvell claims it is providing a easy path to adapt to changes in the 802.11g spec. For example, several months ago when the IEEE 802.11 committee made changes to slot time operation in the draft 802.11g spec (for example, backoff time dropped from multiples of 20 μs to multiples of 9 μs). Marvell accounted for these changes with adjustments to firmware embedded on the ARM. By keeping pace with the current spec, Chen said Marvell can avoid the potential compliance and interoperability issues faced by other chip developers.

Flexibility in the ARM processor can also provide power savings in the overall system. Clock frequency on the ARM9 processor can be adjusted in 44 MHz steps, Chen said, thus allowing designers to reduce clock frequency to reduce overall system power consumption. Overall, when implemented in a CardBus system, the chipset can achieve power consumption figures down to 300 mA, he added.

The 88W8510 and 88W8310 handle the baseband and MAC tasks required for 802.11g and b operation. Both chips also include a hardwired security block that can handle AES functions as well as the counter CBC MAC algorithm, two key security elements specified under the 802.11i standard. To make the 88W8510 friendlier for an AP environment, Marvell also added a 10/100 Ethernet MAC, a 10/100 Ethernet physical layer block, a flash interface, and an SDRAM interface to the IC.

The 88W8010 RF front-end IC works with both the 88W8310 and 88W8510 baseband chips. Similar to the 802.11b front-end IC, the 88W8010 combines an RF transceiver and CMOS power amplifier in the same package. The power amplifier can deliver a +23-dBm output at the antenna in 802.11b and a +20-dBm output power in 802.11g applications. The transceiver, on the other hand, is developed aro und a superheterodyne architecture and can deliver between -71 to -73-dBm sensitivity levels when employed in 802.11g applications, Chen said. The transceiver also embeds additional circuitry that eliminates the need for an external surface-acoustic-wave filter from the board, Chen added.

Marvell is sampling the chipset to early access customers. Volume production of the chipset is expected in mid 2003.