Wireless HD Gaming Over UWB

By Jeff Goldman

September 01, 2005

Pulse~LINK and Analog Devices say the combination of their technologies is a low-latency boon for gaming and beyond.

Last week at the DisplaySearch HDTV Conference in Beverly Hills, Calif., Pulse~LINK and Analog Devices demonstrated live transmission of a high-definition video game, encoded using Analog Devices' ADV202 JPEG2000 codec, over a Pulse~LINK CWave ultrawideband (UWB) link between an Xbox and a television. The demonstration was intended to showcase the strengths of both CWave and JPEG2000 for real-time wireless high-definition gaming.

Bruce Watkins, Pulse~LINK's President and COO, says the key benefit of CWave and JPEG2000 in this instance is extremely low latency.

"Low latency is very important in a video game application," Watkins says. "You don't want there to be any delay between, say, playing your video game, moving the joystick, and firing your weapons button."

Unlike the encoding process for JPEG2000, Watkins says, the MPEG encoding process inevitably creates latency. "Even if you had a very expensive, professional MPEG encoder, it would still encode about a half a second of latency," he says. "And for your consumer-grade encoders, it can be as much as one to three seconds of latency."

Latency, Watkins says, is also an issue of the Media Access Controller (MAC) itself. "You couldn't just throw JPEG2000 on top of, say, Wi-Fi, and do this," he says. "It's not a matter of the bandwidth — it's a matter of the latency the MAC induces. Our analysis of other ultrawideband MACs at the present point in time is that there's a latency issue there as well."

Watkins says CWave is uniquely positioned to resolve this issue. "We had to develop a gigabit MAC to handle a gigabit wireless data rate, and some of the things we needed to do to optimize for speed in the MAC also delivered a very low-latency solution," he says.

Analog Devices' solution, Watkins says, is also far cheaper than a comparable MPEG encoder. "It costs about $10,000 to do real-time MPEG encoding," he says. "For Analog Devices' silicon, you're talking in the $25 range: it's very low-cost."

It's not just applicable to wireless gaming. "If you wanted to go wirelessly from, say, a laptop computer to a flat panel on your wall, the last thing you want is to be typing on your keyboard and have the characters come up on the screen one to three seconds later," Watkins says.

A second demonstration involved transmission of video content from a DVD player, encoded with both MPEG compression and JPEG2000. "The demonstration showed the resiliency of JPEG2000 in a wireless channel," Watkins says.

With MPEG encoding, Watkins says, an increase in the bit error rate immediately causes blocky digital artifacts — while JPEG offers a more graceful degradation. As the bit error rate increases, you might gradually notice a decrease in quality with JPEG2000, but you'll have a viewable image for far longer than you would with MPEG.

A third benefit of using CWave UWB with JPEG2000, Watkins says, is scalable encoding. Rather than having to compress a stream so much that you inevitably lose clarity, JPEG2000 allows you encode at any ratio you like. "You can have an exact representation of the original source content — and that's the same equivalent function of a DVI or HDMI cable," he says. "So what we're showing is a roadmap to a DVI/HDMI cable replacement."

John Santhoff, Pulse~LINK's CTO, notes that the solution's low latency helps in this regard as well. "Because the latency is so short, you can see how the control of feedback to adjust the bit stream rate is possible, because the feedback is very close to one or two frames — instead of MPEG, where if you waited a few seconds, the quality of the link would already have changed," he says. "So you can, in essence, have a very controllable, scalable bit stream advantage because you have the low latency as well."

Regarding the WiMedia Alliance's recent announcement of efforts to promote global acceptance of its own version of UWB, Watkins says the conflict between Pulse~LINK's CWave UWB, part of the UWB Forum's DS-UWB solution, and the competing WiMedia MB-OFDM UWB technology, is often overstated in the media. "WiMedia is pursuing Wireless USB: that's a different kind of application," he says. "I'm quite certain it'll be successful, and there are some very fine companies pursuing that. What we're pursuing is something entirely different. So whether WiMedia is out next month or in three quarters, really, doesn't matter a hill of beans to what we're talking about here. It's a different application."

Brooke Crossley, Marketing Manager at Analog Devices, says her company is agnostic on the UWB standards issue. Analog Devices is also a member of the WiMedia Alliance, and Crossley says, "We expect that they will also be successful in wireless video. In fact, JPEG2000 is equally well applied to any of these solutions."

Bill Bucklen, Product Line Director for High Speed Converters at Analog Devices, says the next step lies in getting JPEG2000 broadly accepted as a leading solution for wireless gaming and similar applications. "People are assuming that MPEG will do it — until they actually try to do it and discover how hard it is, how expensive it is, and how poor the results are," he says. "Then they see that JPEG2000 solves their problems. So I think we're going to have a very interesting market opportunity here in all of these symmetrical applications."

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