Sonus Networks' Support of HD Voice Sets Stage for Accelerated Market Adoption

VoIP Industry Leader Adds Major HD Voice Codecs to Seamlessly Interconnect Different High-Definition Voice Endpoints and Services

WESTFORD, Mass. , February, 14, 2011 – Sonus Networks, Inc. (Nasdaq: SONS), a market leader in next-generation IP-based network solutions , today announced support for key HD Voice codecs in the latest software update to its GSX9000 High-Density Media Gateway , NBS5200 Network Border Switch, and PSX products. Sonus's HD Voice functionality provides the seamless interworking between HD Voice codecs that enterprises and service providers need to offer a unified HD Voice service. It also eliminates unnecessary transcoding by passing HD calls through the network, which retains the original call quality. With this functionality, people can communicate in HD Voice, regardless of which HD phone they use. One of the top five mobile operators in Europe is currently running a trial of Sonus's new software to support an HD Voice service for its mobile customers.

As Sonus has many of the largest carriers in the world among its customers, this new software creates an immediate and significant on-ramp for these companies to implement HD Voice-ready networks. In fact, by opening this road for HD Voice to its installed base, Sonus is enabling a significant percentage of the market to immediately offer this service to their subscribers.

Enabling so many global operators to become HD Voice-ready through their Sonus deployments addresses one of the major hurdles to HD Voice adoption and use. While HD Voice offers significant benefits in terms of crisper, clearer conversations and better comprehension, users can only communicate in HD with other people who are on the same HD network or who are using the same HD Voice codec, such as 3G callers with AMR-WB. This restriction creates "islands" of HD Voice users, a fragmentation that prevents the technology from being adopted widely. By supporting the important HD Voice codecs, Sonus bridges these "islands" and creates a unified, seamless HD Voice service that allows any user to reach any other user on any network in crystal-clear HD.

The key HD Voice codecs that Sonus supports are ITU-standard G.722, the oldest of wideband voice codecs, and AMR-WB, also known as G.722.2.

"Like many early technologies, HD Voice has been hampered by vendors using different codecs for their equipment without any transcoding support in the network. This has kept most people from using the service, as it restricted who they could reach in HD," said Joe McGarvey, principal analyst, IP Services Infrastructure at Current Analysis. "It's basically like buying an HDTV that can only get HD video on a few channels. As the industry works toward a standard HD Voice codec, Sonus' new HD Voice transcoding, combined with the company's installed base, takes the technology a giant step forward."

In an increasingly globalized society, HD Voice plays a critical role because it delivers richer, more nuanced conversations. This improves a listener's comprehension, helps to identify speakers on conference calls, improves the understanding of accents and prevents inaccuracies and misunderstandings. Service providers can use HD Voice to improve customer satisfaction and retain customers. Enterprises benefit from improved speech recognition in call centers and other noisy environments as well as text-to-speech applications. Aside from improving the quality of general business and personal conversations, HD Voice is viewed as a cost-effective way for broadcasters to eliminate ISDN lines and reduce the need for in-studio interviews.

Each time a call is transcoded from one codec to another, however, the quality degrades. By passing through HD calls without transcoding, or by properly transcoding between different HD codecs, Sonus keeps call quality high. In addition, Sonus HD Voice intelligently re-orders the codecs when setting up SIP sessions to align them with the end points of the call, and supports sessions that involve a mix of HD and non-HD endpoints, such as conference calls. Without Sonus' solution, calls on different HD Voice codecs will default to a poorer quality, non-HD call.

"Users are beginning to expect high-quality, cross-network conversations to any device - from a Skype client to 3G smartphone or IP phone at an enterprise - just as they expect high-quality TV pictures," said David Tipping, vice president of marketing and product management, Sonus Networks. "By including a unified HD Voice solution in a simple software upgrade, we are hoping to accelerate its adoption and make its benefits widely available."

Sonus HD Voice is available in Release 8.1.0 for the GSX9000 and PSX and on Release 2.0 for the NBS5200. It can be included in new purchases of the company's GSX9000 High-Density Media Gateway , NBS5200 Network Border Switch, and PSX products.

About Sonus Networks

Sonus Networks, Inc. is a leader in IP networking with proven expertise in delivering secure, reliable and scalable next-generation infrastructure and subscriber solutions. With customers in over 50 countries across the globe and over a decade of experience in transforming networks to IP, Sonus has enabled service providers and enterprises to capture and retain users and generate significant ROI. Sonus products include media and signaling gateways, policy/routing servers, session border controllers and subscriber feature servers. Sonus products are supported by a global services team with experience in design, deployment and maintenance of some of the world's largest and most complex IP networks. For more information, visit www.sonusnet.com .

This release may contain forward-looking statements regarding future events that involve risks and uncertainties. Readers are cautioned that these forward-looking statements are only predictions and may differ materially from actual future events or results. Readers are referred to Item 1A "Risk Factors" of Sonus' Annual Report on Form 10-K for the year ended December 31, 2009 and all subsequent Quarterly Reports on Form 10-Q, which identify important risk factors that could cause actual results to differ from those contained in the forward-looking statements. Any forward-looking statements represent Sonus' views only as of today and should not be relied upon as representing Sonus' views as of any subsequent date. While Sonus may elect to update forward-looking statements at some point, Sonus specifically disclaims any obligation to do so, except as required by law.

Sonus is a registered trademark of Sonus Networks, Inc. All other company and product names may be trademarks of the respective companies with which they are associated.

For more information, please contact:

Aline Kaplan
alkaplan@sonusnet.com
+1 978-614-8167

Paul Roberts
sonus@daviesmurphy.com
+1 781-418-2418