networkZONE Products for the week of August 19, 2002
Marvell Says . . .
Two Chips, No Waiting Marvell's Two-Chip 802.11b Solution
Makes WLAN Cards, Gateways, And APs Affordable, Versatile, And Available
Now
Highly Integrated Libertas Chipset Removes Performance Impediments
and Security Bottlenecks While Offering Advanced Features to Allow the Industry
to Massively Deploy "Worry-Free" WLAN Connections
Marvell has solved the critical issues that have hindered the widespread
adoption of wireless LANs by offering the industry's first complete, two-chip
802.11b wireless LAN solutions. The Marvell Libertas 88W8300 baseband/MAC
processor and 88W8500 single-chip access point (AP) solutions can each be
individually combined with the industry's most integrated radio frequency
(RF) transceiver chip, the 88W8000, for 2-chip client and AP applications,
respectively. Both chipsets have been optimized to provide unprecedented
levels of performance and new features that will make 802.11b wireless LAN
a standard feature in enterprise infrastructures, laptops, home gateways,
as well as consumer electronic devices.
"Our goal is to accelerate and broaden the appeal of wireless LAN solutions to the general market. This can only be achieved by offering a solution that enhances performance and eliminates shortcomings in current solutions," stated Weili Dai, Marvell's Executive Vice President and General Manager for the Communications Business Group. "We focused on building features that would make wireless LAN operation a 'worry-free' experience - it should just work in all environments. This will give our customers the confidence that their products can be safely and reliably built into platforms for the mass consumer."
Key features which have been built into the 88W8300 and the 88W8500 include improvements in range, battery management, interference immunity, and security. The all-CMOS Libertas 88W8300 and 88W8500 chips each have advanced Digital Signal Processing (DSP) technology to lessen the impact of various phenomenons that occur in wireless transmissions. One important effect is multi-path, which can severely reduce range and lower transmission speeds. As a result, the Marvell Libertas solutions will have up to a 4x better multi-path tolerance in most environments than current competitors. Established wireless connections also become more robust and are less likely to experience dropouts as users move between different locations. These range performance increases are also heightened when coupled with the Libertas 88W8000 RF transceiver chip, which provides the industry's highest receive sensitivity and most powerful on-chip, power amplifier (PA) output power at 20dBm at the antenna connector. The end result is a solution that easily out-distances competitive solutions by 2x.
"In addition to high performance, the Marvell Libertas solutions include additional advanced features, providing enhanced capabilities for wireless LAN systems," stated Lawrence Tse, Marvell's Vice President of Wireless Engineering for the Communications Business Group. "Marvell has incorporated auto-programmability into our on-chip power amplifier to provide better power-management and extended battery life. We have also optimized our industry-leading DSP technology to provide more interference immunity to co-channel 802.11b interference, allowing for increased speeds and functionality in realistic wireless LAN deployment scenarios. Last, we have dedicated hardware to perform advanced IEEE AES encryption, providing the industry with the most secure wireless LAN connections."
In addition to chipset offerings for client and access point applications, Marvell also provides complete hardware and software reference designs to accelerate customers' time-to-market. "Our complete reference designs make it easy for our customers to implement Wireless LANs as a must have capability in various market segments," stated Dr. James Chen, Wireless Product Marketing Manager for the Communications Business Group. "To this end, we are announcing reference designs such as mini PCI for laptops, PC cards for retail markets as well as Compact Flash for PDA applications. Tying all of these clients together are our Access Point (AP) reference designs which will allow APs to be deployed more cost-effectively and more densely than ever before."
Libertas 802.11b Client Chipset Solution
For client applications, the Marvell Libertas chipset solution comprises
the 88W8000 RF transceiver and the 88W8300 baseband processor/MAC, and includes
the following features:
Libertas 802.11b Access Point Chipset Solution
For access points, the Marvell Libertas chipset solution comprises the 88W8000
RF transceiver and the 88W8500 Access Point chip. It offers most of the
above features plus the following:
analogZONE Says . . .
So while the 802.11a/g debate rages, the majority of products in the shelves at Fry's and Staples today are the plain vanilla 802.11b 11-Mbit units which will serve the needs of 90% of today's users quite nicely. It seems that Marvell has adopted a similar product strategy in the release of its latest WLAN chips. Instead of trying to anticipate the market, they are optimizing their current products to fill the existing market better. Their new Libertas chip sets are aimed squarely at the 2.4-GHz, 11-Mbit market with an eye towards making WLANs a standard feature in akin to 10/100 Ethernet in laptops, handhelds, and other applications.
While the siliconistas at Marvell have certainly used high levels of integration to reduce the BOM cost of a WLAN radio to the point where it's a no-brainer to include it as a standard feature, they have not neglected features, or performance. I'm glad, especially about performance, since I think that some chip makers' relentless focus on cost-cutting is resulting in products that seriously under-perform on 802.11's promises.
They have come out with two chip sets - one for client applications, and one for use in broadband gateways and access points. The client and AP chip sets have specialized baseband chips, but they both use the same RF chip, the 88W8000 RF transceiver which was introduced earlier this year as part of Marvell's first 802.11b chip set. It is a relatively straightforward architecture (see figure), except that it makes use of lots of on-chip passives to minimize external components and has an on-chip power amplifier - more on this later.
As I said earlier, the Libertas uses external passives sparingly. It uses on-chip LPFs in the TX and RX paths, and only uses one shared external SAW in the IF path, plus a single external crystal oscillator. An inexpensive external ceramic filter cleans up the on-chip PAs signal feed. I reviewed it in my former life at ChipCenter and was fairly impressed, although I had some reservations since it was still in tape-out then. I'm pleased to see that the RF chip is now in full production, and have fewer (but not zero) worries about whether it will deliver as advertised.
The baseband chips are where Marvell has used its expertise in SoC design to cram nearly everything necessary for the intended applications. Besides nearly identical baseband processing circuitry, both chips have an ARM-9 core for running some of the MAC and security functions, The hefty RISC engine has a good bit of remaining power for user apps and customization as well. The current version even runs at a reduced clock rate (8300 runs at 44 MHz), allowing it to be upped in future versions to support new protocols or user applications.
Beyond this, the 88W8300/88W8500 are optimized for their given applications. The access point chip for example, includes a complete 10/100 MAC & PHY - an industry first that cuts the cost and complexity for both broadband gateways, and wireless access points (see figure). Like Marvell's stand-alone transceivers, it even includes auto-negotiation and auto-polarity (eliminates need for crossover cables), features that will cut calls to a manufacturer's product support hot line dramatically.
The client-side MAC/Baseband chip is designed to work with all of the popular host interfaces, including USB, GPIO, Ethernet, PC Card/CardBus PCI/Mini PCI, and Compact Flash (see figure) It also sports integrated SRAM to further cut costs, although it - still needs an external EPROM or flash or download from host.
If Marvell is to be believed (and I have reasonable cause to do so), they have given at least as much attention to building in solid performance into their chip set as they have on making it inexpensive and easy to turn into a complete product.
Range is at the top of my list for must-haves in WLAN products. Besides wanting to be able to wander to my neighbor's house with my laptop running, I know that good reach is critical in the unpredictable, and occasionally hostile environments that occur in both professional and non-professional installations. Marvell covers this with excellent receive sensitivity and the most powerful on-chip PA on the market (+20 dBm at the connector, 22 dBm at the chip.)
I am still somewhat skeptical of on their-chip PA, in part because of how hard it is to produce an efficient, and linear high-power device in CMOS, and mostly because of the havoc that high-powered RF can play with sensitive mixer and VCO circuits. After a long talk with Marvell (and the fact that the chip is actually shipping) I'll concede that they may have delivered on what they promised to do. They build the 88W8000 RF chip in CMOS with a MIM capacitor process and employ heavy isolation between the PA and rest of chip to keep the noise problems to a minimum. The isolation includes a separate 2.2-V supply for the PA that runs below the 2.5-V supply used by the rest of the chip.
Another critical performance is multi-path tolerance - a real serious issue, especially in large open offices and industrial spaces with lots of hard metal surfaces. Marvell claims that their equalization techniques can converge an almost unrecognizable signal using a low-power signal processing engine. They say that it lets the receiver tolerate up to 680 ns delay spread at 11-Mbit/s link rate, and more at lower speeds. They were annoyingly tight-lipped about the details of this element of their design other than to say that they developed a highly-accurate model of interference & multipath environments and used it to test various equalization approaches before committing to silicon. I suspect that they are pretty credible here but since they withheld critical details, I'll have to leave it up to you whether to believe them.
They were equally tight-lipped about their approach to improving immunity to co-channel interference. This is most likely to happen when two or more unrelated WLAN networks are running on adjacent channels in close proximity to each other (e.g. multi-tenant office building or apartment complex.) Marvell says it uses its proprietary DSP technology and CCA (clear channel assessment) to look at the transmit environment to assess the ability to transmit on the basis of more than just whether there is energy in the channel. On the receive side, they claim to do some sophisticated filtering and EQ to allow it to function with lots of adjacent channel signals. Once again, I cannot vouch for their claims.
Battery life should be more of a given than a feature for WLAN cards, but Marvell seems to have made a few extra efforts to sip lightly on a laptop's vital juice. Their self-adjusting power amplifier controls its output level based on multiple factors so it uses just enough power to reach its destination with a clean signal. Besides the normal RSSI, the chip uses the noise environment, and traffic loading to calculate and adjust its dynamic range from 0 to 20 dBm in 1-dB increments. Since transmit comprises only a few percent of the transceiver's duty cycle, it's a good thing that other power saving modes can be invoked to put most of baseband/MAC chip into various levels of inactivity. This will be especially appreciated in PDAs and other handheld devices which pack much smaller batteries than laptops.
Like battery life, security stuff is a must have. And Marvell has it. Client security features include support for de facto 40/64-bit and 104/128-bit WEP, as well as the soon-to-be-finalized 802.11i AES protocol. Programmable elements will accommodate details still in flux (key management and other protocol issues) so that even existing products will be upgradeable.
The 8300 & 8500 Baseband./MAC chips are currently in Alpha sampling, with 8000 in full production.
While exact pricing seems to be as big a secret as the workings of its equalizer, Marvell was able to tell me that the volume price of the client chip set will run in high teens, with the AP chip set in low $20s. This should result in a very Sub-$25 BOM for a PCI card-based client product. And almost as important, the extreme attention to detail, plus a good reference designs and supplied software should give designers a short time to market.
While Marvell is mum on the topic, I expect that we'll see the next spin of the Libertas family will be a home networking oriented product, with the baseband chip sporting multiple 10/100 Ethernet ports and a small layer-2 switch. They are also unwilling to disclose details about when they will introduce an 802.11g solution, but I expect to see it as soon as the standard quiets down a bit. All Marvell will say about an 802.11a radio chip is that it is in progress for next year.
With both chips in production, I'm lowering the Vapor Index Rating significantly over my previous review. I've added a half-saltshaker however, to account for my reservations about the aggressive integration used in the RF chip, and Marvell's unwillingness to discuss some of the more sensitive architectural issues with me.
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