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Multimedia: Wi-Fi or UWB?

While some have painted ultrawideband as a Wi-Fi killer, industry insiders generally concede that there's room for both technologies in the wireless networking landscape. However, there's one area of the market that may not be big enough to handle both: multimedia.

It wasn't so long ago that the idea of delivering high-quality video and audio streams over wireless networks seemed like little more than a pipe dream. Yet a number of companies have already developed products that stream music and images from a PC to a home entertainment center using Wi-Fi. Now, companies are starting to focus on DVD- and HDTV-quality video, and for that, some UWB insiders argue, Wi-Fi just doesn't cut it.

"Wi-Fi really wasn't built to move audio and video," said Matthew Shoemake, CEO of Allen, Texas-based UWB startup WiQuest Communications, and the former chair of the IEEE 802.11g and 802.11n Task Groups. "It was built for data traffic where if there's delay, jitter or dropped packets every once in a while, the network recovers and the end user typically doesn't notice."

UWB is better suited for multimedia for a couple of reasons, he argued. For starters, its throughput far surpasses that of Wi-Fi. The spec being developed by the Multiband-OFDM Alliance calls for data rates of up to 480Mbps at a range of 2 meters, and 110Mbps at 10 meters. Compare that to Wi-Fi, which currently tops out at 54Mbps.

While several companies have developed proprietary speed boosts for Wi-Fi, and a higher-speed version of the standard -- 802.11n -- is in the works, Shoemake said that increasing the speed of 802.11 won't be that easy.

"Every time 802.11 pushes up the physical layer rate, they'll have the additional problem that the efficiency will go lower. People are having to do awkward things at the MAC layer just to get the efficiency up. If you have a 108Mbps physical layer the MAC efficiency is getting very poor, so end users may only experience 30, 40, 50Mbps."

Since the MAC for UWB was designed for high data rate and low power, he said, the efficiencies are much higher -- 80 to 90 percent compared with 40 to 60 percent for 802.11g. That means speeds of up to 432Mbps for a UWB physical layer based on 480Mbps.

Aside from bandwidth, quality of service (QoS) is also a concern with Wi-Fi. While the upcoming 802.11e amendment will address some of these concerns, Shoemake contends that it won't be enough. "They have a very difficult problem given all of the legacy devices that are already out there and all the legacy mechanisms that are used, and trying to create an efficient network given all of the baggage that has to be carried along."

On the other hand, he noted, the MAC for UWB was designed from the ground up with QoS in mind. Its excess amount of data rate can help maintain quality, as well.

Meanwhile, Wi-Fi executives counter that 802.11 is more than capable of carrying video, and that the industry is making improvements all the time.

"It is possible to do high-quality video with Wi-Fi," said Ciricia Proulx, director of marketing for Toronto-based ViXS Systems. She pointed to the company's demonstration at the CES tradeshow in January as an example.

"We were running on our floor, in the middle of our booth, with hundreds of bodies passing through, two simultaneous HDTV signals over our Matrix chipset, and it didn't fail the entire show. That's about as challenging an environment as you can get, I think."

The Matrix chipset is an 802.11a processor that uses two channels to transmit video streams. Using 802.11a avoids potential interference with cordless phones and microwave ovens (or even 802.11b or 802.11g networking gear), which operate in the 2.4GHz range. Anselmo Pilla, a product marketing manager at ViXS, said the chipset runs at between 35-40Mbps on each channel, for an aggregate result of 70-80Mbps (that's actual throughput).

That's more than enough for delivering high-definition video streams, he argued, which are typically around 20Mbps. Standard-definition broadcasts range from 3-6Mbps. Until people start buying multiple HDTV sets for their homes, Wi-Fi will be sufficient, said Pilla.

Regardless of the type of wireless network, Proulx said, the ability to adjust bit rates, formats and resolutions is paramount to achieving quality video streams. "I don't care if you're Wi-Fi, UWB or powerline," she said, "the link is invariably going to be subject to impact. To guarantee QoS and the kind of experience customers are used to, you need to deal with the video."

ViXS addresses this issue with its Xcode chipset, which can transrate and transcode multiple video streams on the fly, ensuring that the video bit rate always fits within the available network bandwidth while preserving the frame rate and the quality of the viewing experience.

Proulx pointed to UWB's short range as a drawback. "Yes they've got a lot of capacity very close to the device, but it's not going to deliver whole home coverage, and people aren't going to buy a multitude of devices to spread all over their house," said Proulx.

While future versions of UWB may extend its range, she noted that by that point, Wi-Fi may be firmly entrenched in the market. As it is, UWB chips are still months away from shipping. Products using the technology aren't expected to appear until next year.

"The reality is that Wi-Fi is delivering multimedia right now," said Proulx. "When you go at a well-established standard with multiple suppliers that has become highly cost-effective, it's really hard to pull it off."

One place where UWB could outshine Wi-Fi might be in its ability to deliver large amounts of data uncompressed. Kurt Scherf, vice president and principal analyst at Parks Associates, suggested that in the context of the ongoing digital rights management (DRM) debate, UWB might be an attractive technology to companies who want digital content to remain uncompressed between set-top boxes and displays.

"They want it to be such a large file that people are going to find it very difficult, if not darn near impossible, to copy it to some kind of media," he said. "If that happens, it's going to require a solution with the robust throughput of UWB."

Still, Scherf thinks that Wi-Fi and UWB can still work together. Noting UWB's short range, he noted that it could be used as a cable replacement technology in cluster networks, while Wi-Fi covers the area as a whole.

"I think in a world of the future, you might see Wi-Fi and UWB working as cooperative technologies where UWB covers the very high throughput requirement between a set-top box and a digital display or HD screen, and you might use Wi-Fi as a whole house transport medium."

However, he added, "over the short term, it's a Wi-Fi world."