Case Studies

2 www.radisys.com RADISYS CUSTOMER STORY | Improving VoIP Conference Quality Experiencing echo problems while hosting VoIP audio conferences, a leading provider of IP-based communications services was at risk of failing to satisfy service level agreements (SLAs). The service provider sought a solution capable of delivering high quality audio, comparable to the Public Switched Telephone Network (PSTN). "Our customer enabled the voice quality enhancement software on existing media servers, which simplified the deployment, lowered their CAPEX expenses andleveraged deployed systems without introducing new elements to the network." — David Smith General Manager, Media Service Business Unit at Radisys Two Architectural Approaches The service provider evaluated two vendors, both having a different architectural approach to integrating voice quality enhancement (VQE) into the network. The first vendor solution was based on a specialized, dedicated single purpose network element situated between subscribers and the core of the network. The solution had two major drawbacks: a high price per line, and the expense and complexity of adding a dedicated network element. The vendor pricing model required the service provider to pay for echo cancellation on every line, although only 15-20 percent of the lines typically need it at a given time, according to industry studies. The second solution added VQE software to the Radisys Convedia CMS-9000 Media Server, the currently deployed IP media server in this service provider's network. Since it wasn't necessary to add a new network element, which typically increases end-to-end call path delay, the solution was better equipped to address voice quality issues. In fact, the echo cancellation performance of the CMS-9000 Media Server met all the requirements of the service provider. Furthermore, the solution perfo rms dynamic echo cancellation on a subset of lines—the problematic lines— thus reducing license fees and the load on the server's CPUs. Compared to the first vendor solution, the Radisys CMS-9000 Server delivered higher voice quality at about one-fifth the cost, after accounting for dynamic echo cancellation and deployment on an existing server (e.g., no extra hardware). Higher Audio Quality Radisys' integrated VQE technology cost-effectively overcomes voice quality challenges associated with an IP packet network, thereby increasing end-user satisfaction in VoIP conferences. The solution implements various mechanisms to address the common sources of audio quality problems, including audio noise, dropped packets and echo. The following describes just a few of the voice quality enhancement features. • Problem 1. Audio noise coming from background sounds like dogs barking, planes flying overhead and people conversing nearby. • Solution: Prevent unnecessary noise from being inserted into a VoIP recording or conference mix by attenuating (e.g., decrease amplification) the noise without impacting the voice signal. • Problem 2. Dropped (or delayed) packets caused by congested IP networks. • Solution: Synthesize audio with a prediction based on previously received packets, when there are audio gaps, using a technique called packet loss concealment. • Problem 3. Acoustic echo, an irritating echo of someone's voice, created when sound emanating from the receiver's speaker (e.g., handset or speakerphone) is transmitted back by the receiver's microphone. • Solution: Compensate for the variable delay inherent in VoIP networks using sophisticated echo cancellation algorithms.

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