The rise of packet voice

People who knew the operator who placed the very first transcontinental phone call in the US are still alive today. So are people who had party lines, four-digit phone numbers and used operator assistance for interexchange calling. At the other end of the spectrum are people who have used cell phones atop the highest mountains and made calls from places where explorers launched polar expeditions 100 years ago.

Communications and telephony have made great strides in a single lifetime, and it's not over yet. But with trillions of dollars of assets tied up in the public switched telephone network (PSTN), questions about next-generation voice services are financially critical. It's less a question of whether things will change (they already have) than of how those changes can be accommodated.

PSTN consists of voice services based on time-division multiplexing (TDM). Just as packet-based data services have largely replaced circuit-switched data, packet voice is expected to replace TDM voice.

The primary drivers behind the shift to packet voice include:

• The high cost of PSTN switching;
• Increased competition from over-the-top (OTT) competitors using packet voice;
• The evolution of mobile services to 4G (which, unlike 3G, lacks a circuit-switched voice channel);
• Fixed-mobile convergence (FMC) and femtocell deployment; and
• Enterprise pressure to adopt IP voice delivery (such as SIP trunking).

Taken together, the timing and magnitude of these drivers will determine the likely makeup of next-generation voice services.

The over-the-top voice driver is the most dramatic and, in many ways, the most relentless. Broadband wireline and wireless deployment create a "new dial tone" in the form of Internet access.