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UWB finds place in wireless HD videos

Posted: 08 Sep 2008 ?? ?Print Version ?Bookmark and Share

Keywords:wireless ultrawideband? UWB? HD video connection? HDMI?

Since the Federal Communications Commission gave wireless UWB the go ahead in 2002, proponents have pushed the technology as a way to wirelessly distribute video in the home. Over the years, however, UWB IC vendors rarely delivered on promises and the technology fractured into different camps. Finally, it appears that wireless UWB products will ship based on announcements at the CEDIA show taking place in Denver this week.

UWB isn't about to distribute video around the entire home via a wireless link, but it may finally offer an alternative to the HDMI cable. Tzero Technologies senior director of marketing Dave Borison states, "UWB is better than wired HDMI." Borison claims TZero's technology can cover 20- to 30m in range compared to typically 2m HDMI cables. The wireless alternative offers a plus in terms of input flexibility, but remains very expensive for now.

A/V specialist Gefen, which sells primarily to home theater installers, just announced two products that replace an HDMI cable with a wireless link. Note a subtle distinction in how companies such as Gefen or UWB IC vendors describe such products. Almost universally, the companies call the products "Wireless for HDMI." The HDMI Licensing organization controls the brand and there is no official Wireless HDMI standard. Instead companies such as Gefen develop HDMI extenders that work over a variety of media including wireless links and Cat 5 cable.

High alternative cost
At CEDIA, Gefen announced one Wireless for HDI Extender based on a UWB chipset from TZero. TZero relies on the WiMedia flavor of UWB based on an OFDM channel. The Gefen product definitely offers advantages over an HDMI cable that connects an HD source to an HDTV. The consumer can more conveniently locate source and TV with a wireless linkespecially given the typically short HDMI cables. Moreover the TZero-based design includes multiple HDMI inputs and legacy component HD inputs. So essentially, the product also functions as an HDMI switch connecting multiple HD sources over the single wireless link.

The price is the bad news. At launch the transmitter/receiver pair will sell for around $700 limiting the market to high-end home markets. The price is driven by more than the cost of the UWB radio. The transmitting unit must encode the uncompressed HDMI or component video output so that it can be transmitted over the wireless channel where the receiver can then decode the stream.

Meanwhile, Amimon has been touting its 5GHz-based technology as another option for wireless HDTV video distribution. The company claims uncompressed HD video transmission as one of its key advantages. At CEDIA, Gefen also announced a Wireless for HDMI Extender product based on Amimon ICs and it appears that the Amimon product will carry a similarly high price tag.

The Amimon claims of transmitting uncompressed video may not withstand close scrutiny. Pulse~Link CTO John Santhoff pointed out that Amimon's claim of delivering 3Gbit/s data rates in a 20MHz channel exceeds the limits of Shannon's Law. Amimon has described a method of not transmitting parts of an image frame that would be unimportant to the human eye. That description makes it tough to discern the difference between how Amimon handles a stream relative to MPEG compression.

Pulse~Link also offers a UWB-based Wireless for HDMI technology that's being adopted in televisions by Westinghouse. Pulse~Link relies on their proprietary Continuous Wave flavor of UWB. The Westinghouse TV units aren't presently shipping but Pulse~Link president Bruce Watkins claims the units will be on the market in the next few months. Pulse~Link, like all of the players in the Wireless for HDMI area had been waiting for the Digital Content Protection LLC to endorse their scheme as an Approved Retransmission Technology. The company got the approval at the end of July.

Will it go mainstream?
Still there's a question as to whether the cost of wireless HD implementations can ever come down to levels that would drive it into the mainstream. The issue goes back to the question of whether the wireless link carries compressed or uncompressed streams. HDMI proponents have long claimed that content owners demanded uncompressed connections. Realistically, the content owners have endorsed the Digital Transmission Content Protection scheme over links such as IEEE 1394 or FireWire.

Amimon is counting on a perceived preference for uncompressed transmission by content owners and their belief that consumers will reject compression-based products. Realistically, consumers only care about quality. It will be interesting to see the Wireless for HDMI candidates side by side in the coming months to see who if anyone has a quality advantage. Any successive encoding/decoding operation always degrades quality to some extent.

Going to a fully compressed distribution scheme would eliminate any quality concerns. As Santhoff points out, "you can't find an uncompressed source." Santhoff is correct that all feeds from Blu-ray players, HD satellite receivers, HD cable boxes and even HD camcorders arrive as a compressed stream. There is no real reason that the compressed stream shouldn't be carried all of the way to the display and decoded a single time at the display.

The compressed scenario pays dividends in terms of price and performance. The much lower bit rate of the compressed stream will always be easier to transmitregardless of the wireless or wired channel in use. And the UWB radios could quickly drop in price if the encoding/decoding functions were eliminated. TZero's Borison claims his company could offer just the UWB radio chips in the range of tens of dollars for integration into STBs and TVs.

- Maury Wright
Digital Home DesignLine

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