Ruckus patents technique for video over Wi-Fi

The system turns multicast video into unicast streams so it can run more smoothly

Wi-Fi equipment vendor Ruckus Wireless has patented a technique that appears to be widely used to improve video on wireless LANs.

The company recently received patent protection in Europe after earlier having it patented in the U.S. Many other vendors seem to use a similar approach, according to industry analysts. But Ruckus said it isn't going on the warpath.

"We're not looking to go out and sue the industry," said Seamus Hennessy, Ruckus' chief financial officer.

"We want to use this to build a case and build a strong patent portfolio, so if we do need to go on the offensive, we can," Hennessy said.

The technique is a fundamental one involving a shift from one transmission protocol to another, and Ruckus said its patent is broad. In 2004, when it was trying to develop wireless LAN gear that could smoothly deliver high-definition TV, the Ruckus engineering team found a problem: Carriers used multicast to deliver IPTV (Internet Protocol TV), and multicast wasn't suited to 802.11 networks.

Multicast is an IP mechanism that sends one packet to multiple endpoints, in this case subscribers' TVs. That works on wired networks, but on wireless LANs, every endpoint needs to receive a given stream of packets at a different speed based on its distance from the access point, as well as other factors. In addition, with multicast, wireless LAN endpoints have no way of acknowledging to the access point that a packet has been received.

In response, the network slows down the multicast session to the lowest common denominator to reach the most distant endpoint. Under those circumstances, the video can be choppy or slow.

Ruckus already had special antennas and software to make high-definition video run more reliably over wireless LANs, but this problem stood in the way.

"It became clear to us that the way 802.11 handled multicast wasn't going to work at all," said Bill Kish, Ruckus co-founder and chief technology officer.

The problem could affect enterprises that distribute training videos or other content to employees over a wireless LAN, as well as any other application that uses multicast in a home or office, Kish said. That includes push-to-talk on Wi-Fi pagers such as those from Vocera, he said.

In response, Ruckus devised a way to first detect when an endpoint was trying to initiate a multicast session and then change that session to one using unicast, another IP transmission system. Unicast sends a separate stream to each endpoint, so each session can run at the correct pace for that endpoint, and sends acknowledgments for incoming packets.

Unicast puts a bigger load on the network because it sends a separate video stream to each endpoint. But even with heavier traffic, unicast delivers a better video experience than a multicast session that isn't working, Kish said.

The multicast-to-unicast conversion is the only real option for any vendor that wants to make multicast run well over its networks, and the technique is widely used, said Burton Group analyst Paul DeBeasi.

"I don't think anyone's doing anything fundamentally different," DeBeasi said. "I would bet that the vendors would look closely at the patent."

Within enterprises, multicast over wireless LANs is not widely used, analysts said. But service providers are just beginning to embrace IPTV, and most consumers receiving that programming will want to use a wireless LAN to distribute it through the house, said analyst Craig Mathias of Farpoint Group.

"If you make the assumption that video goes all-IP over time, then this is an important technology," Mathias said.

Used properly, patents are a way of contributing intellectual wealth to a society, Mathias said. Companies that use them to attack other companies for what may be unintentional infringement are abusing the system, he said.

"You should only consider legal action when there's absolutely blatant infringement," Mathias said. He expects Ruckus to do the right thing. "I don't think that Ruckus is a litigious firm," he said.

Privately held Ruckus, founded in 2004, is still dwarfed by Wi-Fi rivals such as Cisco Systems. Ruckus has 240 employees and had 2008 revenue of US$32.9 million.

The company got its start making gear that service providers can set up in subscribers' homes to distribute high-definition video, though it has expanded its scope to go after enterprises as well.

On Monday, Ruckus is announcing that its equipment is distributing video on demand wirelessly to guests at a newly renovated hotel in Philadelphia. The company and Kimpton Hotels, which runs the Palomar Philadelphia, claim this is the first such deployment in the world.

When the historic Art Deco hotel was renovated recently, the rooms were equipped for high-definition video on demand over Ethernet. But later, some rooms were reconfigured and the Ethernet cables couldn't reach the repositioned TVs in 97 out of the 230 rooms. Rewiring or changing the wiring plan would have been costly and time-consuming, said Michael Thibodeau, director of openings and transitions at Kimpton.

Using a Ruckus wireless LAN around the hotel, with adapters in each of these rooms, Kimpton is now streaming the video-on-demand programming to those guest rooms. The property didn't have to be rewired, and now TVs can be set up anywhere in the hotel to receive video on demand, said Sandro Natale, president and CEO of Superclick Networks, which set up the network. Kimpton plans to use a similar approach in a hotel now being renovated in Chicago.

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Stephen Lawson

IDG News Service
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