VoIP: Better than PSTN?
by Jan Linden, PhD
Vice President of Engineering,
Global IP Sound, Inc.
Many factors in the past have slowed the anticipated growth of Voice over IP (VoIP). Now, VoIP solutions that achieve quality and reliability, close to what we are used to from the Public Switched Telephony Network (PSTN), are emerging as the market is quickly growing. However, as will be shown in this article, there is no reason to limit the expectations to achieve only the same level of quality as in PSTN. It is quite well known that by deploying wideband voice codecs much better quality can be achieved. However, a little known fact is that there are ways to achieve better quality than a standard PSTN solution, even when using narrowband codecs. For example, the full available spectral bandwidth is not typically used in traditional PSTN solutions, something that can easily be done in a VoIP system. But implementing a wideband codec or expanding the bandwidth of narrowband codecs does not automatically guarantee great quality. There are many potential pitfalls when deploying VoIP. In this article we also discuss implementation issues related to VoIP that will impact the final voice quality.
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