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WLAN chipset designed specifically to handle video challenges

Posted: 27 Jan 2005 ?? ?Print Version ?Bookmark and Share

Keywords:vixs? wireless video? xcode? video processor? wlan data chipset?

ViXS' vision was to enable wireless video. The company already had its XCODE video processor. Early on, the design team realized that WLAN data chipsets were not sufficient to deliver video, so they decided to design their own.

The most recent result of this focused effort is the Matrix II chipset and its associated WaveTV reference design.

Most video systems are unidirectional, with the majority of data coming from server to client. So, the team at ViXS worked to make the receive end very sensitive. Using a proprietary technology, known as MaxRatio technology, they we are able to take in two signals from the same stream, combine them in the physical layer (PHY), and increase the amplitude of the signal (enabling greater distance and steady bit rate). Other improvements on the receive side included enhanced signal detection (10dB to 20dB performance improvements over other solutions) and enhanced error correction, while still maintaining compliance with the 802.11 a/b/g specification.

How do they do this? "We make it possible to recover more packet errors and avoid re-transmissions," said Anselmo Pilla, senior engineer at ViXS. "I cannot reveal specifically how we do it, but I can say that the error correction circuit enhancement can typically gain 6dB to 8dB."

What about the competition? The team notes that when compared to off-the-shelf data chipsets, the Matrix II offers approximately 2x improvement in rage for wireless video. Ciricia Proulx, ViXS' director of corporate marketing reports that, besides some proprietary solutions, there are "no real standard solutions to compare it to. There are some 'pre-n' non-standard solutions for delivering video, but the Matrix II also uses multiple antennas and is standards based."

In the WaveTV reference design, the Matrix II is paired with ViXS' XCode II MPEG processor. A notable feature of the XCode II encoder is its ability to enable very high quality video at a low bit rate (less than 2Mbps). It ensures video Quality of Service by monitoring and measuring the wireless network in real time, and providing feedback on available bandwidth to the XCode II, which then performs bit rate adjustments on the fly. This ensures the video is always optimized and always fits within the available bandwidth without any frame drops or jitter. The XCode II also enables improved transrating and transcoding, at 8X to 24X, so you can transfer video very quickly, such as a 2-hour movie in 15 minutes, and you can change the bit rate and resolution. So, if you want to transfer to a handheld, you can do it in seconds.

How did they do that? "On a high level, we become really creative in terms of using the existing algorithm for MPEG compression as well as for transrating (decoding and re-encoding the video). We are still standards compliant, but can do high-quality video at low bit rates as well as being able to do multi-streams with one chip," shared Pilla.

The team worked to address its customers' major concerns in the design of the Matrix II:

??? Link stability (being able to keep the link even for a distance of at least 100 ft/through 3 walls, which should cover most homes). "We are getting 30Mbps to 40Mbps, which allows manufacturers to deliver at least two high-definition (HD) streams," noted Pilla.

??? Deliver HD content. "We had been told that other solutions cannot support it, or they provide ad-hoc systems that cut out when you move," Pilla remarked.

??? Standards compliant. "Because they are looking at eventually having systems that support video, audio and data. For data networks, there are already plenty of wireless products available, and they want them to be compatible," Pilla said.

ViXS reports that the Matrix III is already in the works, and it will be compliant with the upcoming 802.11n WLAN specification.

The WaveTV reference design (including the Matrix II chip) is already available (BOM cost of around $50 per side). The Matrix II chip is available for $16 in quantities of 10,000.

- Janine Love


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