Packet-based voice (VoP) has quickly evolved to enable a single network to deliver a new generation of business and consumer voice and data services. Carriers have announced that new network buildout will be based on packet technology that supports a converged network that carries both voice and data. According to Probe Research, the VoP market is expected to grow from 7.7 billion minutes in 2000 to 570 billion minutes by 2005.

Packet-based voice provides several advantages over circuit-switched voice. Bandwidth required for a voice call can be significantly reduced through voice activity detection (VAD) techniques and use of low bit-rate CODECs. VAD removes silence, which accounts for as much as 40 percent of the voice information that is transmitted. Low bit-rate CODECs reduce the amount of bandwidth for a voice call from 64 kbps to as little as 8 kbps.

Based on open standards, a packet-based voice and data infrastructure allows faster time to market for new services and enhancements with third-party developers offering products to service providers. Capital investment for packet-based platforms is significantly less than for circuit-switched equivalents. The savings in operational costs have been estimated at 40–50 percent by carriers based on the consolidation of platforms and network management applications.

In a few short years, packet-based voice has evolved from a technology demonstration to an integral part of next-generation networks and services. The accelerated pace at which this technology has evolved can be attributed to some key factors:

• VoP technology feasibility
• Digital signal processor (DSP)–based technology with low power consumption and scalable channel density
• Enabling transport technologies, e.g., digital subscriber line (DSL), cable
• Interoperability and standards

Early VoP applications were targeted at providing lower-cost long-distance services. One early application was transporting long-distance voice traffic between certain cities that traditionally experienced a high volume of traffic, for example, between Hong Kong and Vancouver. A second early application was carrying voice traffic between corporate facilities on their existing data networks, significantly reducing the voice traffic expenses.

It is clear that a wide range of consumer and business services will be available utilizing packet-based voice as part of bundled voice and data service offerings. VoP gateways are being implemented for a number of applications ranging from small two-port integrated access devices (IADs) for the consumer and telecommuter to very large carrier-class gateways used as Class-5 switch replacements.

Many technical barriers have been overcome to bring VoP technology to its current state. Large-scale VoP networks have become increasingly feasible as DSP–based technology has been refined to provide lower power and higher densities with manufacturers meeting the challenge of interoperability. Silicon and software technology for VoP has evolved to support hundreds of channels and will soon support OC–3 channel density on a single chip (greater than 2,000 channels). This tutorial will focus on understanding the requirements and architecture for high density VoP platforms with an emphasis on the elements required to implement VoP in carrier class applications that will meet the service providers expectations to deliver toll quality voice.