Hi-def flowers

Hi-def goes wireless

The emerging standards battle over wireless HDTV.

The shift to high-definition TV (HDTV) has brought better quality images and sound into our homes. The downside has been the nest of cables that comes with HDTVs, especially when they're used in home theatre set-ups. The consumer electronics industry is working hard to do away with these cables, but so far with little success. Wireless HDTV, it turns out, is a tough nut to crack.

The challenge is to replace HDMI cables with a wireless link from set-top box to TV that will support HDTV signals in the highest quality 1080p format. For an uncompressed video stream, this can require bandwidths of up to 3Gbit/s. The wireless link should also extend around the house, which is a huge challenge. The equipment must be available at consumer prices, and work to a standard. Progress on meeting these goals has been slow.

That may be about to change. A group of TV and equipment makers has coalesced around a technology developed in Israel. In July it launched a new industry group called the Wireless Home Digital Interface. While some large companies are involved, other companies and groups have been working on wireless HD for years and are not going to let this go easily. A standards battle is on the cards.

The Wireless HD consortium, formed in 2006, brought together LG Electronics, Matsushita Electric (Panasonic), NEC, Samsung, Sony and Toshiba around a 60GHz technology developed by SiBeam. This has evolved into a specification for 4Gbit/s data rates transmitted on a 60GHz carrier. The consortium now has 40 companies, mainly Japanese, signed up.

Developing a solution

Around the same time, Philips proposed a variant of the 802.11n Wi-Fi technology, developed by Metalink, as a solution to wireless HDTV transmission. Companies such as Tzero and Pulse-Link have also been developing technologies for a wireless version of HDMI, eventually fighting each other over patents in the courts.

Tzero's technology is now shipping in wireless HDMI devices from Hitachi. Pulse-Link's wireless technology has been adopted as part of the next generation of the 1394 Firewire standard, so that the same protocols can be used across both wireless and wired links.

The 1394 Trade Association has developed a 'no new wires' home-networking standard that offers data rates of up to 800Mbit/s. It should enable high-speed multimedia networks that work with 1394 and IP-enabled devices and which have the bandwidth to transport compressed HD data over wireless or wired Firewire links. The MAC/PHY layers specified in the new standard are available now in a chipset from Pulse-Link that uses its CWave UWB technology, which also offers guaranteed Quality of Service.

"After more than two years of close collaboration with the 1394 Trade Association and its member companies, Pulse-Link is proud to be a part of the first international standard to incorporate UWB over coax," says John Santhoff, co-founder and chief technology officer.

"Pulse-Link's contribution of its intellectual property to this standard opens a true whole-home HD networking experience of 1394 and IP content to consumers globally."

Pulse-Link is also targeting the HDMI market, having demonstrated a wireless HDMI solution using its CWave technology two years ago. This is now coming to market as the cost of the components, notably a JPEG2000 codec from Analog Devices, makes the approach cost effective, says Santhoff.

This means there could be a single protocol from the TV through the entire network, as the new standard also serves as the basis for the whole-home networking backbone defined by the High-Definition Audio-Video Network Alliance (HANA). Many of the guidelines for development of HANA-enabled products will be based on the '1394 over coax' specification.

But now comes the Wireless Home Digital Interface (WHDI). This brings together many of the leading equipment makers - Hitachi, Motorola, Samsung, Sharp and Sony - around a new video modem technology, developed by Amimon in Israel, that can transmit uncompressed HD video in the unlicensed 5GHz band.

The video modem prioritises different parts of the uncompressed HD video stream into different layers, sending the most significant layers over the most robust link with the most error correction, and sending the less significant parts of the video with less error correction.

Variable distances

The modem can squeeze an HDTV datastream into the data rates supported by existing 5GHz technology. The key is that the approach can send uncom-pressed video over short distances from a set-top box, games console or Blu-Ray player to a TV, and over longer distances in the home, elimi-nating the need for a compressed distribution network.

"To have a viable wireless HD communication standard it needs to support uncompressed video, not compressed," says Noam Geri, vice president of marketing and co-founder at Amimon. This is because copy protection, electronic programme guides and overlays tend to be added onto the video stream and so a compressed stream doesn't have the same quality, he says. "The consumer electronics manufacturers will not support something that degrades the performance or quality of the image, so they want uncompressed video."

He points to the problems that 60GHz signals have penetrating walls and floors, leaving it as a short-distance solution rather than one for the whole home. In contrast, the WHDI approach also adds control protocols so that a DVD player downstairs can be controlled directly while watching the output upstairs.

But WHDI is an industry grouping like HDMI, rather than an IEEE standardisation process.

"HDMI is a de facto standard and WHDI will be the same," says Geri. "We are bypassing the entire IEEE and government standards committees."

Geri plays up the potential health advantages of the WHDI approach: "60GHz [as used by the Wireless HD approach] is one of the resonant frequencies of water. That doesn't sound like a good thing, and because of the poor propagation it has to be transmitted at a higher power. Of all the wireless technologies, 5GHz is probably the safest. It's much lower power than 60GHz or cellular phones."

He also points to the technology lead that WHDI at 5GHz has over WiHD at 60GHz, in terms of the air interface, even though it is two years behind with its specification. "5GHz has a 15-year headstart over 60GHz on cost, and we can do WHDI in a single [CMOS] chip," he says.

The group expects a specification by the end of this year with silicon in 2009 supporting 1080p and the control protocols, moving to a single chip in 2010. Pre-compliant WHDI equipment will start shipping by the end of the year, with fully compliant systems in 2009, Geri says.

So how long will it be before the market shakes out and consumers can buy wireless HD systems with confidence? As you might expect, many of the consumer electronic equipment makers are hedging their bets by joining both the WHDI and the WirelessHD camps. The aim is to let the market choose, mirroring the battle between HD-DVD and Blu-Ray. The risk is that the standards battle will hold up the adoption of a wireless HD technology.

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