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Ruckus Wireless Awarded Patent Essential to Running Video, Voice and Other Multimedia Applications Reliably Over Wi-Fi

Monday, December 07, 2009

United States Patent Office and European Patent Office Grant Ruckus Wireless Patent for IP Multicast-to-Unicast Conversion

Sunnyvale, CA -- Ruckus Wireless today announced that the United States Patent and Trademark Office (USPTO) and the European Patent Office (EPO) have each awarded the company a landmark patent on conversion of multicast to unicast transmissions. Originally filed in November 2004, the multicast conversion patent is one of nearly two dozen patents granted to Ruckus with dozens more pending approval.

Multicast, a one-to-many transmission technique for data communications networks, is frequently used for delivering multimedia information to multiple simultaneous recipients. For example, IPTV service providers use it to deliver IP-based broadcast television programming to subscribers over a broadband network; many enterprise applications such as tele-presence and video training also use it.

For 802.11 networks where multicast information delivery is not guaranteed, multicast-to-unicast conversion is essential to providing more reliable transmissions and more predictable performance for loss- and delay-sensitive multimedia applications.

The Ruckus multicast-to-unicast patent is particularly significant to the wireless networking industry as the growing demand for wireless multimedia communications coincides with the rise in Wi-Fi usage everywhere.

What Problems Does Multicast-to-Unicast Conversion Solve?

Many video applications transmit digital information to receiving devices using IP multicast. When transported over 802.11 networks, these multicast transmissions typically use a best-effort technique that requires no acknowledgement from the receiving devices. Without acknowledgments, the wireless system has no way to determine if traffic was successfully delivered, no basis for retransmitting the packet if it was not properly received, and no mechanism to select the optimal physical layer data rate with which to transmit the packet.

Because delivery of multicast traffic is inherently unreliable due to the lack of acknowledgements, most APs simply transmit multicast packets at the lowest physical layer data rate (e.g. 1 mbps) in an attempt to increase the probability of error-free reception. This leaves the multicast traffic more susceptible to interference due to the increased transmission time.

Wi-Fi networks are particularly problematic for multicast due to the higher rate of dropped packets caused by interference, obstacles and other problems. Consequently, multicast transmissions are often rendered unusable for mission critical applications over traditional Wi-Fi networks.

In contrast, Wi-Fi unicast transmissions require acknowledgements from receiving devices. Sending devices can use these acknowledgements to determine the success of transmissions and hence drive 802.11-layer retransmissions while optimizing the physical layer data rates.

By converting multicast or broadcast packets into one or more unicast packets, as described in the Ruckus patent, Wi-Fi systems can now leverage the powerful 802.11 acknowledgment feedback mechanism. This built-in feedback helps to achieve extremely low packet loss rates for multicast traffic while increasing the number of multicast streams that the system can reliably transport.

When combined with intelligent antenna arrays, multicast-to-unicast conversion further enables the Wi-Fi systems to adapt automatically to changes in the signal environment. These systems can use unicast acknowledgements as one of many decision criteria to automatically "steer" Wi-Fi transmissions over the best performing signal paths in real-time.

Ruckus Wireless has commercialized Smart Wi-Fi solutions and remains the only Wi-Fi supplier with systems deployed in more than a million locations around the world, supporting the distribution of high-definition IP-based television over standard Wi-Fi.

"This patent fundamentally improves the quality of service that can be delivered over Wi-Fi networks," said Bill Kish, Ruckus Wireless CTO, co-founder and one of the named inventors. "New applications for Wi-Fi are quickly appearing as performance and reliability increase. There is incredible demand for wireless that is as reliable as a wire. Ruckus is taking it there."

The multicast-to-unicast conversion, part of the Ruckus SmartCast quality of service engine, is integrated within Ruckus Smart Wi-Fi products. SmartCast comprises a variety of traffic handling and quality of service technologies specifically developed to improve the transmission of delay-sensitive traffic over 802.11 networks dramatically.

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