PRISM Jumps to 140Mbps

By Eric Griffith

January 07, 2004

Another chip makes the leap to super-high speeds, promising to work with legacy WLANs and avoid pitfalls its competitors have encountered.

The latest chipmaker to announce an over-100Mbps speed jump is GlobespanVirata of Red Bank, N.J, which says its current PRISM Nitro products will see throughput pushed to 140Mbps by the end of the first quarter of this year.

According to Jim Zyren, the company's director of strategic marketing, the speed boost, called PRISM Nitro MX Xtreme Multimedia, works using a "shopping list of features." It is meant for use with video and audio over wireless LANs in the home market.

DirectLink is what Zyren calls the cornerstone technology of Nitro MX. He says the hardware automatically creates a connection between clients or from a client to a media source, such as a media server, and avoids the access point. It does this while staying in Infrastructure mode so the client can continue to utilize AP-based security and power-savings.

"The access point negotiates a side session," says Zyren, "you negotiate with the access point but don't pass the data through it."

He says DirectLink by itself will double the throughput of a PRISM Nitro chipset.

Other technologies involved in getting 140Mbps are packet bursting (a form of which is used by all the current speed boosts from chipmakers like Broadcom and Atheros, and is based on technology slated for the 802.11e specification) and compression of files.

"If I'm transmitting a large text file, the savings [with compression] can be significant. If it's data already encrypted and random and scrambled, there's no meaningful compression," says Zyren.

Use of the Nitro MX technology is automatic between equipment and won't require any user intervention to activate. Nitro MX hardware will communicate with older 802.11 products at the standard speed of the specification.

PRISM Nitro technology will be available on GlobespanVirata's 802.11g PRISM GT chips, and the PRISM WorldRadio (formerly called Duette), a dual-band 802.11a/b/g chipset. Netgear and SMC Networks and some overseas manufacturers are currently shipping products using PRISM Nitro. It will be up to these original equipment manufacturers (OEMs) whether to provide the final MX Xtreme upgrade to end-users.

Competitors Atheros and Broadcom have recently been in the news as Broadcom claims that Atheros Super G technology harms nearby networks when using a channel bonding technology. GlobespanVirata says its own tests concur with that assessment. Zyren says his company is avoiding that problem by staying with a single-channel solution.

"We don't hurt legacy systems," he says. "If Nitro MX is on channel 1, and someone nearby is on channel 6, it will not collide."

The 2.4GHz band used by 802.11b and 11g only have 11 channels for use in the United States, but only three of them do not overlap: 1, 6, and 11.

Despite these issues, all the companies have reportedly been successful selling their non-interoperable speed boosts.

The PRISM line of chips originated with Intersil, which became the leading supplier of 802.11b silicon. GlobespanVirata bought the PRISM products last year and is poised to merge with Conexant, perhaps as soon as the close of the first quarter of this year. The combined company will retain the name Conexant and will be based in Red Bank.

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